The original puzzle may be found here.
Lots of great clues here with a good variety which covered nearly all bases. 14A was excellent, as were 25A and 22D. 1A and 27A were impressive anagrams.

| ACROSS | ||
| 1 | WALPURGIS NIGHT |
Right wing pals assembled outside university, April 30th (9,5)
|
| (Right wing pals)* around u{niversity} | ||
| 10 | AUDIT |
Check gold and diamonds investment after being cleaned out (5)
|
| Au(=gold symbol) + d{iamonds}(=abbrev used in playing cards) + i[nvestment]t | ||
| 11 | NASHVILLE |
City finish off Aston Villa – he’s getting sacked (9)
|
| ([Asto]n Villa he’s)* | ||
| 12 | PROXIMO |
President features in video plug next month (7)
|
| Xi(=Xi Jinping, current Chinese president) in promo(=video plug) | ||
| 13 | NARWHAL |
Ran around with young Prince Harry, the horny beast! (7)
|
| Ran< + w{ith} + Hal(=nickname often used for Harry) | ||
| 14 | THE UNTOUCHABLES |
Costner led its cast – lowest cast, by the sound of it (3,12)
|
| Hom of lowest caste, referring to the dalit or untouchable caste in Indian society. | ||
| 18 | CHARLES GOODYEAR |
US chemist‘s rosier update on “Elizabeth: annus horribilis”? (7,8)
|
| CD i.e. Charles having a good year as opposed to Elizabeth having a bad one. | ||
| 20 | ELUSIVE |
Difficult to catch scoop paid out ten cents (7)
|
| E[xc]lusive (removing X(=ten) c{ents}) | ||
| 23 | DOCKERS |
500 uncultured Aussie blokes who emptied a few schooners? (7)
|
| D(=500 in Roman numerals) + ockers(=slang term for uncultured Australian males) | ||
| 25 | SACRISTAN |
The Devil claims Sir Charlie, retired church worker (9)
|
| Satan(=the Devil) around (sir C{harlie})<. Charlie is C in the phonetic alphabet. | ||
| 26 | ALL IN |
Dropping to the floor naked, absolutely knackered (3,2)
|
| [F]allin[g] | ||
| 27 | ANTIDEPRESSANT |
Doctor patented an SSRI drug (14)
|
| (Patented an SSRI)* | ||
| DOWN | ||
| 2 | ANDROMEDA |
Star group‘s uncovered landau touring airfield (9)
|
| [L]anda[u] around {aero}drome. The def here refers to the star constellation. | ||
| 3 | PUTTI |
Chubby lads in Lilliput, titchy (5)
|
| Hidden in Lilliput titchy. The def is the plural of putto, a word for a winging cherub often depicted as chubby. | ||
| 4 | RANCOROUS |
Managed my no-frills accommodation, full of bitterness (9)
|
| Ran(=managed) + cor(=my!) + [h]ous[e] | ||
| 5 | IBSEN |
Norwegian playmaker starts for Ipswich, bags three points (5)
|
| I[pswich] b[ags] + SEN(=three compass points). Ibsen was of course a playwright rather than a footballer. | ||
| 6 | NEVERLAND |
Final appearance of Ian Lavender working US ranch (9)
|
| ([Ia]n Lavender)*. The def refers to the ranch formerly owned by Michael Jackson. | ||
| 7 | GALAH |
Brave knight left adult daughter a pretty cockatoo (5)
|
| Galah[ad](=Sir Galahad losing a{dult} d{aughter}) | ||
| 8 | TRELLIS |
Climbing frame exhausted Trevor Peters (the novelist) (7)
|
| T[revo]r(=exhausted referring to losing contents) + Ellis (Peters), the pseudonym of the novelist responsible for the Cadfael mysteries. | ||
| 9 | CARPET |
Reprimand moggy, having crapped inside on a regular basis (6)
|
| Cat(=moggy) with even letters of crapped inside | ||
| 15 | NULLIFIED |
Rendered invalid, I’d suffered with Nile flu (9)
|
| (I’d Nile flu)* | ||
| 16 | CLOG DANCE |
Measure fit for wooden shoes? (4,5)
|
| CD – a measure is a type of dance. | ||
| 17 | LLEWELLYN |
Nelly getting excited when cuddling fit Welsh lad (9)
|
| Nelly* around well(=fit) | ||
| 18 | CHELSEA |
Part of Tuchel’s earlier team (7)
|
| Hidden in Tuchel’s earlier | ||
| 19 | RESENT |
Begrudge papa leaving here (6)
|
| [P]resent (papa is used as the P in the phonetic alphabet) | ||
| 21 | UNCUT |
Like a rough diamond when sober? (5)
|
| CD/DD. Cut can mean drunk, so uncut by extension would be sober. | ||
| 22 | ESTOP |
European turning over a fortune in bar that’s legally approved (5)
|
| E{uropean) + pots<(=a fortune). Estop is a legal term for preventing something. | ||
| 24 | CRASS |
Boorish Conservative, right idiot (5)
|
| C{onservative} r{ight} + ass(=idiot) | ||
Very much appreciated the appropriate surface of 27ac (ANTIDEPRESSANT) and the &lit-ish feel of 18dn (CHELSEA) given that Thomas Tuchel did manage that side in 2021-2.
Excellent stuff. I’d only come across WALPURGIS NIGHT in the German before. CHELSEA is nicely &littish.