Financial Times 12904 / Phssthpok

I have been blogging every Tuesday since March 2008 but this is the first time I encountered a puzzle by Phssthpok.
I enjoyed solving this crossword, which is of average difficulty.
At the end of the alloted time, three clues remained to be solved – they are all in the bottom right corner.

Across

1 PIERCING – hom. of “peer sing”
5 SCRAWL – s, crawl (stroke, term. from the sport of swimming)
10 SWALLOW – sw(all)ow -‘flying backwards’ in wordplay is a rev. ind.
11 OPPRESS – op, Press
12 OASTS – (-b)oasts
13 NECTARINE – anag. of ‘entrance I’
14 CIVIL SERVICE – solved from def. – wordplay seems to suggest that ‘something done politely for us can easily be returned’ (one good turn deserves another?). Am I missing something here?
18 POET LAUREATE – anag. of ‘operate a lute’ (‘badly’ being the anagrind); I think grammar requires that it should read … “operates a lute” since the subject is “Betjeman or Wordsworth” but I will stand corrected if I am wrong.
21 LOVEBITES – love, bites (“is effective”)
23 Not solved
24 PROVISO – not “pro, viso(-r)” but “pro viso(-r)”
25 UNALIKE – Una, like
26 ESTEEM – E, ‘steem’ (rev. of ‘meets’)
27 REVENGES – I know that ge (rev. of e.g.) is the content in this c/c clue, I also see that ‘clerics’ could give Revs. but I have not sussed out the rest of the wordplay.

Down

1 PASTOR – past, or – I thought “forgotten” for ‘past’ was not quite exact. Things that are bygone are not necessarily forgotten.
2 ELAPSE – E(laps)E – E for Ecstasy (drug) – drugs = drug, drug, E,E
3 CELESTIAL – I got this from def. and hazily from wordplay, which I see just now – ‘estia’, anag. of ‘a site’ (“in flux” being the anagrind), in ‘cell’ (“space”)
4 NO-WIN SITUATION – I think this is anag. of “snow in situ” plus at, ion, “position is hopeless” being the def. No, No. I have just realised that this is a long, hidden clue that was long-hidden for me!
6 CUPPA – Cu(p,p)a
7 APERITIF – a, peri, tif<
8 LISTENER – L, is, tener (anag. of ‘enter’) – How are we to deal with “to”?
9 WORCESTER SAUCE – ‘Worcester’, I know; ‘sauce’, I know, but ‘Worcester sauce’ is new to me; anagram of “wet racecourses”. – What are we to make of “in”? ‘In’ can be a connector to a def. but can it be a connector to anag. fodder?
15 RATIONALE – ration (v. “dole out”), ale – “Excuse” does not seem to be quite an apt synonym for ‘rationale’.
16 APPLE-PIE – two def.? – ‘apple-pie order’ is ‘perfect order’; will ‘apple-pie’ in itself give “order”?
17 LEAVE OUT – leave, out
19 Not solved
20 Not solved
22 BRIBE – “Carrot” is def. (as in “carrot-and-stick policy”), “bachelor” will give B – I don’t see the rest of wordplay.