So, on to the puzzle itself. The title is a single question mark
(?) The preamble tells us that the wordplay in all, except 8,
clues lead to an extra letter and the remaining 8 contain a single extra word.
The extra letters define the theme word and the extra words lead to the
“component parts” of the thematic items. The thematic
items themselves (4 of them) are to be entered around the perimeter, unclued of
course. And the theme word has to be highlighted in the final grid.

So, the perimeter spelt out EGGHEADS,
UNIVERSITY CHALLENGE, MASTERMIND and ONLY
CONNECT. All of them are QUIZ programmes on BBC TV,
though I’ve never heard of, let alone seen, ONLY
CONNECT. So, QUIZ is the theme word. The extra letters
spell out BANDALORE, BIT OF BANTER, HOAX and MOCKING
LOOK, each of which is a definition of QUIZ.
QUIZ has to be highlighted in the grid reading left to right
from the centre square.

The 8 extra words (and the component parts they define, nicely in orer) are:
MINE:EGG,
FACILITIES:HEADS, ACADEMY:UNIVERSITY, DISPUTE:CHALLENGE, SEASON:MASTER,
DISLIKE:MIND, JUST:ONLY and
ASSOCIATE:CONNECT.

We found the cluing to be fairly easy and it didn’t trouble us too much,
despite the beer. The only query is 30a YO-HO.

Across

7   PHILATELY: PHI [anagram of HIP] + LATELY
8   QUICK: double definition ['quick' = 'living' as in the Apostles' Creed]
9   POSTERIOR: double definition
10 KNELT: cryptic definition
12  MEMORY: reversal of ROME in MY: I took a stupidly long time over this, looking for a reversal in ‘my reminiscences’.
13 APPRAISE: reversal of PA [pop] + PRAISE
16  SEGMENT: G MEN [FBI agents] in SET [placed]
19  CRACKER: double definition [or two!]
22 ALLIANCE: ALL + anagram of NICE [Edit : A NICE - thanks, Arfanarf!]
25  STRESS: S[econd] TRESS [lock]
27  SLIPS: double definition: I hadn’t thought of ’slip’ implying ‘quickly’: Chambers has ‘to move quietly, easily, unobtrusively or stealthily’ and Collins ‘to move or cause to move smoothly or easily’.
28  APPOINTED: POINT [reason] inside APED [taken off]
29  BENCH: double definition
30  GINGER ALE: GI [soldier] + anagram of GENERAL: great surface!

Down

1  CHOOSE: C [a hundred] +  O ['a hole'- I don't think I've seen this before] in HOSE [socks]
2   PLATFORM: double definition: this was the last one in. I expected it to end in ‘ism’, while I was still being blind about 12ac.
3   STOREY: TORE [rent] in S[hrewsbur]Y: another great surface
4   ALSO-RAN: cryptic definition
5   DUENNA: DUE [expected] + reversal of ANN
6   SCALES: double definition
11  SPAR: double definition: the almost obligatory Rufus nautical clue, with, again, an excellent surface
14  INK: thINKing
15  EAR: alternate letters of rEpAiRs
16  SPA: S[outhern] PA [Pennsylvania]
17  GAL: [le]GAL
18  NINE: cleverly hidden [and clued] in womaN IN Evening
20  CORONARY: anagram of CARRY ON  + O [oxygen]
21 DESPAIR: anagram of SPIDER: another lovely story-telling surface, referring to Robert the Bruce being inspired by a spider to try for the seventh time. [Edit: or, rather,  'A SPIDER' - thanks, Andrew! ]
23  LILIES: cryptic definition
24  IMPACT: I[one] MP [member] ACT [take part]
25  STOOGE: anagram of GOES TO: another fine surface
26 SHELLS: HELL [inferno] in SS [ship]

“Thare are five mistukes im this centence”
True or False?

*=anag, []=dropped, <=reversed, hom=homophone, cd=cryptic definition, dd=double definition.

Common crossword abbreviations this week:

left = L
European = E
king = R
son = S
ring = O
artist = RA

Across

1   A STRAW IN THE WIND: ASTRA [RAF stars] + THE in WIN WIN ['win win situation for the' - I loved that!] + D [500]. The motto of the RAF is ‘Per ardua ad astra’: ‘Through hardship to the stars’.
9   ORANGE PIP: ORANG [ape] + reversal of PIPE
10  FLING: double definition
11  GO TO SEA: T[he] in GOOSE + A
12  AIR BASE: AIR [tune] + homophone of BASS [low notes]. [Of course, base also means low but I think a homophone is indicated.
14  HOGWASH: WAS in place of ART in HOGARTH [William, 1697-1764, moralist painter]
17  ELEGIST: ET [Latin 'and'  'keeping' LEGIS ' of the law in Latin']: reference to Thomas Gray’s ‘Elegy written in an English churchyard’ [1750]
19  PODESTA: ODES in PTA [Parent Teacher Association]
22  STRANGE: ST + RANGE
25 GWYNETH: I don’t want to tread on any toes here, especially considering my ‘thing’ about homophones. It was my understanding that Gwyneth [ the girl] and Gwynnedd [the county] are pronounced the same but I’d be really glad of enlightenment.
26  SYNOVIA: SYNO[d] + VIA
28 ODOUR: I wasn’t too happy with this: I haven’t seen ‘odour’ meaning this unless followed by ‘of sanctity’! Odo, the half-brother of William the Conqueror, was bishop of Bayeux and probably commissioned The Tapestry. [Is UR another candidate for the bonfire?]
29  IN THE CLUB: double definition
30  SATURATION POINT: AT IO in SATURN + POINT

Down

2  TRAIT: homophone of TRAY [carrier]: ‘originally’, because, in English usage, the T in this French word is perhaps more often pronounced.
3  AUGUSTA: AUGUST + A: I’m not very happy with the construction of this clue.
4 IMPEACH: I + MP [1000p] + EACH [apiece]
5   TOP RATE: TO PRATE [nicely balancing 30ac.]
6    ENFORCE: hidden in greEn FOR CEremony
15  GIDDY GOAT: reverse anagram of TOGA: I really like these but I know they’re not everyone’s cup of tea.
16, 24, 13, 1dn SET THE CAT AMONG THE PIGEONS: I jumped in a bit too quickly here and entered ‘put’ instead of ’set’, going purely by the enumeration, instead of working out the anagram [of MATE'S GONE CHEETAH SPOTTING] but Hogarth, on the second pass, put me right!
18, 24. 8 LET THE DOG SEE THE RABBIT: T[ime] in LETHE [forgetfulness] + DO + G[ood] + SEETHE [be very angry] + RABBI [minister] + T [model] : superb charade!
20 SHEARER: S[ociety] HEARER
21  ATHEIST: AT HEIST: I really liked this one.
22  SESOTHO: anagram of TO SHOES: a Bantu language, one of the eleven official languages of South Africa and national language of Lesotho.
23  RUN DEEP: I know I could see this last Saturday but it means nothing this morning: help, please!
27 VALLI: ALL in VI: Alida Valli starred in Carol Reed’s ‘The Third Man’.

The title and individual referenced did indeed match that referred to in Inquisitor 1108, though in quite a different manner.

The precision of the clue writing meant that progress was rapid. This is an excellent introduction to this type of crossword, and has enabled me to gain familiarity with the blogger’s toolset rather than fret over the clues.

I started with the downs as they promised to yield the subject. The first few solved quickly (FH,RI,ES) showed that the first and last letters of the down clues needed to be read as 2 columns and not sequentially eventually giving FREDERIC CHOPIN HIS BICENTENARY. A quick look at Wikipedia yielded a birth date of 1st March 1810 – so accurate to the date of publication too. He was half French and half Polish, hence the title. It also yielded the following somewhat interesting misinformation “[Chopin] was a Jamaican composer and mediocre pianist. He was one of the great masters of Reggae music.” – Not an issue a reference book would have.

Then a similar exercise to resolve the across clues, additional letters in the wordplay yielded ALL WORKS INCLUDE A PIANO 

 So what of the unclued entries – the preamble hinted that these described the bulk of his work, so a musical theme became apparent:  PRELUDES,  POLONAISES, IMPROMPTUS were relatively easy to spot, a quick check of Chopin’s famous works yielded the others. All had a cross checked P (for piano) inserted CONCEPRTO, ETUDPES, MAZURPKAS, SONATAPS, NOCTURPNES, BALLADPES, WALTZPES.

That begs the question, Was it too easy? Possibly for the old hands, but its construction, to my eyes anyway, is flawless, and lacking in any ambiguity. Also, it utilises  four of the commonly used variants in this type of crossword – missing letters, extra words, unclued thematic entries and solution modification.

KEY
Bold – definition element of clue Underline – Extra word (Downs only)
* = Anagram
dd = double definition
Rev. = reversed

Edits thanks to Mike