Thanks to all who gave this a try. Here are the solutions, setters’ names and references to the original threads.
As a point of note, I had to edit a couple of the original clues, one (6D) because it was written as an across clue and in the grid it was a down clue, so ‘back’ became ‘up’; and another (11A) because the original challenge required wordplay to generate an extra letter, so in this case ‘trail’ (a synonym for traipse) became ‘to worship’ (apologies to Darla, as the original clue is far more ingenious!). As I said earlier, I also couldn’t resist cross-referencing 22 and 24, as the two Mad Hatter references emerged purely by chance (original clues given below).
ACROSS
9. A galaxy far away from a Dan Dare novel (9)
ANDROMEDA
Marty PR 500
10. Magazine clip (5)
PUNCH
Tyke CL 474
11. Head off to worship to go higher (5)
RAISE
Darla CL 533 (edited)
12. Six inch lumber and it's all trimmed at both ends, and in position (9)
INCUMBENT
Aristo CL 216
13. Who exploited Bob Marley, his partner? (7)
SCROOGE
Marty PR 267
14. A lettuce maybe found off the shelf (7)
ICEBERG
Dorrien WPR 119
17. Is American-backed drug the problem? (5)
ISSUE
PaulH WPR 107
19. Box of film for film festival audience (3)
CAN
Jono CL 545
20. A teen, awkward and worried (5)
EATEN
Mattrom WPR 74
21. Lord! Never-ending greed, and eaten by it (7)
GRANDEE
Aristo PR 387
22. Mad Hatter and Alice finally showed up here (7)
THEATRE
Fiery PR 516
24. Mr. T had tea brewed for him? (3,6)
MAD HATTER
Paul PR 365
26. React badly to a little touch (5)
TRACE
Marty PR 443
28. Lion swallows book slowly (5)
LENTO
Paul PR 318
29. In thunder we are holding our pants! (9)
UNDERWEAR
Nemo PR 355
DOWN
1. Blonde female with cropped hair (4)
FAIR
Marty CL 631
2. More challenging grid, complicated with setter’s vowels (6)
EDGIER
Jono PR 505
3. Over the hill and far away, spot the local fox hiding (4,2,4)
GONE TO SEED
Ginge CL 330
4. Gadget is shown back to front and gutted (6)
DEVICE
Penda CL 462
5. Prohibit or allow (8)
SANCTION
Chris CL 470
6. Mother with codicil turns up digital junk (4)
SPAM
Seamus, Ayrshire PR 192 (edited)
7. Milan football team is in Paris for benefit (8)
INTEREST
Patrich CL 568
8. Drunkard downs hard liquor (4)
SHOT
Skyewalker PR 381
13. Feeling the heat but not appearing to worry or waver (5)
SWING
Ginge PR 434
15. Real men, yet simple when sorted (10)
ELEMENTARY
Greedy Kite CL 147
16. Pruning evens out greeneries revealing variety (5)
GENRE
Jono WPR 56
18. Paying for the G and Ts in turn (8)
STANDING
Fiery WPR 98
19. Copper with a case he's cracked? (8)
CHESTNUT
Mattrom PR 408
22. Desperately tried to accept onset of alcohol abuse (6)
TIRADE
Malcolmxword WPR 26
23. To proceed, turn right initially, leading into avenue, then left at the end (6)
TRAVEL
Spike PR 386
24. Spot reversal of exacting limitations on military leaders (4)
MOLE
Fiery CL 295
25. Scrap half the alphabet (4)
ATOM
Buddy PR 588
27. Obtain prime seafront locations (4)
EARN
Buddy CL 637