Took me a while to spot what was going on and I found the bottom half tougher than the top, but once I’d twigged the drinks-related theme, everything fell into place. A nice touch to have the thematic answers as downs too!

ACROSS
1 BIRTHDAY I was extremely lucky to cotton on to the theme at the very first clue. Harold Pinter (1930-2008) is such a well-known playwright who has even won the Nobel Prize for Literature and I have see a performance of The Birthday Party before. The well-known broadcaster, Robin Day (1923-2000) with his signature bow-tie confirmed the answer althought I haven’t unravelled John’s gas.
5 CHAPEL Cha of Chap (fellow) EL (an elevated railroad)
9 COCKTAIL Cha of COCK (prepare to shoot) TAIL (follower) and the allusion to The Cocktail Party by T.S.Eliot
10 LABOUR What an absolutely lovely clue that got me rolling on the floor. Before a mother gives birth, she must undergo labour pains.
12 POLYPHAGOUS Ins of GO (become) in *(happy soul) A new word for me meaning adj (of an animal) eating many different kinds of food; given to eating excessive amounts of food, esp as the result of a pathological condition.
15 COACH A coach party and to coach is to train
17 ROSE APPLE an E Indian tree of the clove genus; its edible fruit. I can see Rose as got up but pupil as apple? Anyone?
18 ENLIVENER ENLI *(line) + VENER (worship or venerate minus ate)
19 THIRD Third in a race is still a placing and someone else is a third party
20 ARCHANGELIC ha
24 BOTTLE Welcome to the Bottle Party for people with courage (bottle)
25 TIVERTON TI (rev of IT) VERT (green) ONCE minus CE (Church of England)
26 DOGGED dd
27 TEA PARTY Ins of APART (separated)in TEY (rev of yet, but)

DOWN
1 BACKPACKER Cha of BACK (support)  PACKER (1977 cricketing circus)
2 RECALLABLE RE (King in Italian language) + ins of ALL (everything) in CABLE (TV provider)
3 HET UP Cha of HE (very masculine) TUP (ram, sheep)
4 ANIMATRONICS Ins of MATRON (nursing officer) in *(is I can) Nicholas Wulstan “Nick” Park, is an English filmmaker of stop motion animation best known as the creator of Wallace and Gromit.
6 HEAD START Ins of ADS (publicity) + T (Henry Ford’s Model) in HEART (middle)
7 POOP A party poop is a spoilsport and poop is the stern of a ship
8 LARK dd
11 CONSERVATIVE Ins of AT IV (four) in CONSERVE (jam) for the Tories
13 OPHIOLATER Cha of OP (opus, work) H (hard) I O (round) LATER (in due course) a person who worships snakes … new word for me
14 MENDICANCY MEND (repair) + ins of CAN (vessel) in ICY (cold)
16 HAVE A CLUE Ins of C (first letter of calf) in A VEAL (a calf) to form AVEACL which is inserted into HUE (shade)
21 GEE UP to proceed faster; to encourage, stimulate, buck up; (as interj) a command to a horse to move on or go faster
22 ABED A (first letter of AT) BED (bottom of sea)
23 STAG S (first letter of self) TAG (day in German) a party for men only, esp one held for a man about to be married.

Key to abbreviations used
dd = double definition
cd = cryptic definition
rev = reversed or reversal
ins = insertion
cha = charade
ha = hidden answer
*(fodder) = anagram

I like several clues, but I don’t have a special favourite this time.

Legend to solution comments:
*  =  anagram.

Across
1.	BEDFORD		BED + FOR + D
5.	MORI		MO + RI; Missouri and Rhode Island, ref: Mori poll
9.	NEAR THING		(THE GIN RAN)*
10.	MINCE		C in MINE
11.	MAJOR		dd
12.	LOOK ROUND		LOOK + ROUND; ref: butcher’s hook = look (cockney rhyming slang)
13.	A SHROPSHIRE LAD		(HARDSHIP SO REAL)*
16.	CLUMBER SPANIEL		LUMBERS in (PELICAN)*
19.	SATURNINE		(SUNNIER AT)*
21.	BIGHT		BIG + H + T
22.	CHEAT		E in CHAT
23.	INEBRIATE		(A BEER IN IT)*; an appropriate anagram
24.	GLEN		L in GEN
25.	TRAPEZE		homophone of EASE after TRAP
Down
1.	BONEMEAL		(ONE MABEL)*
2.	DEAR JOHN LETTER		JOHN in DEAR LETTER; ‘penning’ = around
3.	ONTARIO		ON + TAR +R + I + O
4.	DRILL		DR + ILL
5.	MAGNOLIAS		(ANIMALS GO)*
6.	REMORSE		RE + (S in MORE)
7.	INSULATING TAPE		A in INSULTING + TAPE
8.	LEAD		LED around A
14.	ST EMILION		(ONES LIMIT)*
15.	ALL THERE		ALL + THERE
17.	MARITAL		MA + (TRIAL)*
18.	ALBERTA		ALERT around B + A
19.	SACK		dd; cashier also means to dismiss with dishonour
20.	EVENT		E + VENT

Overall, much more accurately-clued than Araucaria’s Saturday crossword two weeks previously. In fact his puzzles vary so much in style from week to week that sometimes I wonder if those published are selected fairly randomly from a portfolio which contains some crosswords he wrote a long time ago. Difficulty-wise it was probably easier than average for this setter.

There was a mini-theme revoving around the Keats poem Ode to a Grecian Urn, whose last couplet is:

     “Beauty is truth, truth beauty,” – that is all
     Ye know on earth, and all ye need to know.

There was a more obscure reference to this poem by Araucaria in this puzzle back in July; this one was probably fairer because these lines are more famous and the wordplays to the thematic answers were helpful (and in 9ac and 8dn, definitions were also included).

Music of the Day (9ac): U2 reference the lyrics in question (’Beauty is truth’) in ‘Playboy Mansion’ but I prefer That Is All by George Harrison, even if it wasn’t Keats-inspired.

* = anagram, “X” = sounds like ‘X’.

I was very lucky in that, after the first pass through the clues, I had ??????O?O?HE? for 1ac and C?N?????L? for 14dn. My immediate thought was that 1ac ended with MOTHER and it wasn’t long before the full answer became apparent. 14dn was then obvious. With these two answers in place, the rest of the puzzle became much easier, though I was unable to get 10dn until I had all the checked letters. It was clearly an anagram of 14dn, as indicated in the preamble, but I failed initially to identify the ‘half word’ as ‘LL.

When the grid was initially completed, the clashes (starting at 30) gave:

                           M/U O U/M S E
G/J O U/V R/U D/L
                           M/U O U/M S E

which could have been resolved as:

           MOUSE
GOURD
           MOUSE

However, this did not take into account the ‘deduction’ and ‘(adding 26 to values where appropriate)’ given in the preamble. Assigning 1 – 26 to A – Z and subtracting the value of the clashing letter in the across clue from that in the down clue (adding 26 to the latter where necessary to ensure a positive integer result) produced:

           HORSE
COACH
           HORSE

This resolution of the clashes was to be entered in the grid and highlighted.

A most enjoyable challenge with a neat twist at the end. It must have taken quite some time to determine the clashes that would give both GOURD/MOUSE and COACH/HORSE, whilst retaining proper words as the initial entries, so thanks Charybdis.

*(XXX) – anagram
[x] – letter(s) unused
{x} – clashing letter

Across
1 FAIRY-GODMOTHER  unclued
12 OCULAR  [j]OCULAR (funny that’s a non-starter) – ‘water pump’ is a humorous term for ‘eye’ and ‘ocular’ is a facetious one 
13 TORC  TO[u]R (series of gigs excluding university) C (clubs)
15 LINGUIST LING (heather) *(SUIT)
17 MAS  MA[qui]S – ‘qui’ = ‘who’ in French and ‘gite’ = ‘mas’ = French farmhouse
18 STOT  S (succeeded) TOT (toddler)
19 OFTEN  OF TEN (in a decade)
20 NOISES  SES[s]ION reversed (period of music-making over, first of singles released)
23 ADD  dd – Attention Deficit Disorder
24 EFTEST  [j]EF[f] (letter concealed by Jeff) TEST (exam)
26 AGAHORS  AGA{m}O{u}S  A GAM (school) OU (where, in French) S[tudent]
29 FULCOAC  FUL{g}O{u}{r}  U (university) L (lecturer) GO in FUR (e.g. ermine)
31 HETOUR  {d}ETOUR  D[iversion] *(ROUTE) &lit
32 DAG  dd – ‘caution’ = amusing person and ‘past sell-by date’ = obsolete
34 SHORSE  S{m}O{u}SE  M[erlin] in SOUSE (pickle) – ‘camelot’ = a pedlar and ‘in The Cape’ indicates South African
36 CLOUD  CLOU (main point of interest) D (departs)
38 TALC  hidden in ‘neaT ALCohol’
40 BOA  BOA[sting] (bragging of having no sting)
41 TURBINAL  T *(RIBU) NAL
42 REBS  REB[el]S (insurgents taking wing)
43 IN ESSE  [f]INESSE (expertise – force not required)
44 PRINCE CHARMING  cd

Down
2 A BIT OFF  A BI (an AC/DC) TOFF (Hooray Henry)
3 RUGOSELY  *(GO SURELY)
4 YOUSE  YO (call for attention) USE (the custom)
5 OUST  [j]OUST (Jack not used in tournament competition)
6 MARTIAH  MARTIA{l}  paRTIAL (favouring) with ‘pa’ changed to ‘MA’
7 ORMOLH  ORMOL{u}  OR (gold) MO LU (two other metals) – molybdenum and lutetium
8 HOSTA  A HOST (poet’s description of daffodils) with the words reversed (preposterous)
9 ERSE  hidden in ‘ovERSEas’
10 I’LL NEED CAR  unclued *(CINDERELLA)
11 IN SITU  SIT (to pose) in [p]IN-U[p]
14 CINDERELLA  unclued
16 TONGCE  TONG{u}E  T (tense) ON (playing) GUE (viol)
21 CAAEAT  CA{v}EAT  CAVE (hollow) AT (administrative trainee)
22 MOTORIUM  MO[ra]TORIUM (Royal Artillery abandons suspension of activity)
25 TONTINE  TON (fashion) TINE (point)
27 RORENT  {m}O{m}ENT  MEN (more than one worker) in MOT (test on car)
28 SUSTAIN  US reversed STAIN (mark)
30 CUDAIC  {j}UDAIC  JUD (Judges) A[pocrypha] I C (see)
33 GOBBI  B (large group of vitamins) in GOBI (Indian cauliflower) – hunchbacks (Italian)
35 HMBER  {u}MBER  dd
37 LEER  dd
39 LUSH  dd

We had ten thematic entries (some with multiple words) plus two words from misprinted defs in clues. These had to be paired and the resulting pairs were clued. It was stated that the pairs were “unlikely to be confirmed in any reference book”. The first part of a pair which I identified was VALET in an unclued answer looking something like ??S?YVALET. I linked this with the clue “The inexperienced servant” to make HOW GREEN WAS MY VALET, a ghastly pun on the 1939 novel by Richard Llewellyn. This (and the title) implied that the pairs were similar puns – a style fairly familiar to me from tackling thematic US-style non-cryptic crosswords. I wondered whether the answers would all be book titles, or members of some other group, but unless I’m being really dense, they’re unrelated. The other five clues and paired answers were:

Rubbish band = TRASH TORC = “trash talk” – a torc is band – a bit of ancient jewellery (TORC and 8D were my last two answers)
Attraction worth looking at = EYEFUL TOWER = Eiffel Tower
Much-loved hat = A FEZ OF THE HEART = Affairs of the Heart
Cheap night for audience = GAWAIN FOR A SONG = Going for a song (night = “knight”)
Supremely confident team = TOTTENHAM CHUTZPAH = Tottenham Hotspur – there may be a little extra joke here, Spurs being the team traditionally supported by North London’s Jewish community.

I’ve only explained about half of the plain clues – ask if any of the others have baffled you.