4 - Bachelor will mark thou problems put down (8) - {BA}{DM}{OUTH*}
8 - Very funny person will do needlework (6) - STITCH [DD]
9 - Concentration in an occupation (10) - ABSORPTION [CD]
10 - Self-images camouflaged in some gossip mongers (4) - EGOS [T]
11 - Bottom of the hydrospace in Thailand (4) - {SEA}{T}
13 - The British head off to chew on this kind of meal (6) - {BR}{
15 - Set back a trailer for a bishop in the direction of an old Iberian kingdom (7) - {NAV<-}{A}{RR}{E} Had to google this
17 - Hard to find the parent, overheard (4) - RARE(~rear)
18 - Say, point to the left of a sleeveless garment (4) - VEST(~west)
19 - Completely discharge the rebellious word used with greats (7) - {ALL}{TIME<-}
21 - Move unsteadily on the rock (6) - TEETER [CD]
22 - Force out the church bird (4) - WREN
25 - Imp supporter is on time (4) - {BRA}{T}
26 - American city now figuring in exotic overalls (2,8) - {EL SALV{AD}OR*} !!! When did the USA occupy El Salvador !!!
27 - Hollow firing place for this source of juice (6) - {O}{RANGE}
28 - I, being French am in good health here out for an hour with an ornament maker (8) - {JE}{WELL}{
DOWN
1 - Elizabeth's ship for once is in the county (5) - {E}{SS}{EX} Was stuck for ages as I read it as Country!
2 - Six excited rogues are not at ease with this activity (6) - {VI}{GOUR
3 - Follow the dance step with regular ease in the east (5) - {CHA}{S}{E} Regular ease is 'e' and 's', how did NJ get only 's' ?
4 - Intoxicate to overcome the love inside (5) - {BES{O}T}
5 - Somehow the bad rule is lasting (7) - DURABLE*
6 - I have followed the robust character interfering (9) - {OBTRUS*}{I'VE}
7 - Cloth set haphazardly covering the hole of the box (4,5) - {TO{O}L CHEST*}
12 - Help a ski resort (5) - {A}{VAIL}
14 - Cotton fabric in the French city (9) - MARSEILLE [DD]
15 - Gone berserk with one in the gallery to work out a deal (9) - {NEGO*}{T{I}ATE*}
16 - Chopper part has a break down alternative (5) - {ROT<-}{OR} Not sure of Anno
19 - Airport landing announcement (7) - ARRIVAL [CD]
20 - Calm leaders set example for philosopher Descartes (6) - {S}{E}{RENE}
22 - Bird will turn away leaving Norway (5) - WA
23 - Slip regularly near the side of the limited fort (5) - {E}{R}{R}{
24 - Stainless metal (5) - STEEL [CD]