This one took me a little longer than usual though progress was always steady apart from a slight hold-up towards the end in the SE corner (though, from what I am led to believe, there are always hold-ups in the SE, particularly on the M25).
I was able to parse all of the clues bar one during the solve but had to return to 18ac whilst writing this post because I had failed to see the anagram fodder (though I did suspect that coarsely was an anagram indicator) or the fact that it was an excellent &lit.
Across
4 Bandage’s length wrapping that woman round (9)
SPHERICAL SPICA (bandage) L (length) around (wrapping) HER (that woman)
11 Grounds to restrict opening of main branch not connected to trunk (7)
MEMBRAL MEAL (grounds) around (to restrict) M[ain] (opening of main) BR (branch)
12 Individual following unknown band (4)
ZONE Z (unknown) ONE (individual)
13 Plant collecting getting paranoid with time, possibly (12)
PTERIDOMANIA an anagram (possibly) of PARANOID TIME
14 Followed former schoolfellow with vision (6)
OBEYED OB (former schoolfellow) EYED (with vision)
16 Unhappy choice of bridge opponents? (4)
SORE S OR E (choice of bridge opponents)
17 Novelist‘s mind surrounded by quiet almost completely (8)
STENDHAL TEND (mind) in (surrounded by) SH (quiet) AL[l] (almost completely)
18 It abrades bits of fir and larch coarsely (7,4)
BASTARD FILE an anagram (coarsely) of IT ABRADES F[ir] L[arch] &lit
20 Cell counted in error (not in the set) (11)
UNCOLLECTED an anagram (in error) of CELL COUNTED
23 Get back and retain plunder (8)
RETRIEVE RET (retain) RIEVE (plunder)
25 Typical corps, wriggling out of ceasefire (4)
TRUE TRU[c]E (corps, wriggling out of ceasefire)
28 Abbey dismissing first trainee (6)
INTERN [t]INTERN (Abbey dismissing first)
29 A messenger pressed a hospital for retraction, getting order to depart (5,7)
APAGE SATANAS A PAGE (a messenger) SAT (pressed) A SAN (hospital) reversed (for retraction)
30 Aircraft / corporation in Scotland (4)
KITE double def.
31 Mistake nasal sound, ignoring weak stimulus to runny nose (7)
ERRHINE ERR (mistake) [w]HINE (nasal sound, ignoring weak)
32 Lubricious poem – The Kiss – found in reference work (9)
OVERSEXED VERSE (poem) X (The Kiss) in (found in) OED (reference work)
Down
1 East German engaged in obscene fraud (9)
IMPOSTURE OST (East German) in (engaged in) IMPURE (obscene)
2 We move on water, interrupted by tense rower (3,3)
WET BOB WE BOB (move on water) around (interrupted by) T (tense)
3 Engineers upset about Eastern potentate (5)
EMEER REME (engineers) reversed (upset) around (about) E (Eastern)
5 Religious attitude not once engaging in spiritless wandering (12)
PRIESTLINESS NE (not once) in an anagram (wandering) of SPIRITLESS
6 Regarding Walesa, say, elevated member of discouraged union? (6)
ELOPER RE (regarding) POLE (Walesa, say) reversed (elevated)
7 Little cash about for housing fellow in prison (6,6)
REMAND CENTRE RED CENT (little cash) RE (about) around (for housing) MAN (fellow)
8 Chamois very good in avoiding peak (5)
IZARD [w]IZARD (very good in avoiding peak)
9 Reluctant fighter that is overwhelmed by shell (7)
CONCHIE CONCH (shell) IE (that is)
10 Birds having dogs losing head (4)
ANIS [c]ANIS (dogs losing head)
15 Break just occurring in other section (9)
ELEVENSES EVEN (just) in (occurring in) ELSE (other) S (section)
19 Strained to keep up, blocking expert move (7)
ACTUATE TAUT (strained) reversed (to keep up) in (blocking) ACE (expert)
21 Tenant not so much keen, being unhoused? (6)
LESSEE LESS (not so much) [k]EE[n] (keen, being unhoused)
22 Tough fabric, sturdy for some, clothing artist (6)
DURANT DUNT (sturdy for some) around (clothing) RA (artist)
24 Received self-confidence, boosted when amongst royal characters (5)
ROGER EGO (self-confidence) reversed (boosted) in (when amongst) R R (royal characters)
26 Irish deny monarchy, promoting knight (5)
RENIG REIGN (monarchy) with the N (knight) advanced (promoting)
27 Dodgy trader upped power, investing pennies (4)
SPIV VIS (power) reversed (upped) around (investing) P (pennies)
Gaufrid, thanks for such a beautifully presented blog (not to mention the wit). Agree about 18 too.
Another Sunday splendidly adorned by The Master.