A few that have currently tripped me up:
18 Across - "Evidence of painful experience in banging performance?"
(6 letters) I have -T-T-- and it seems as if "STITCH" might apply, but I can't see the banging performance part.
13 Down - "Undercarriage scratched in luxury car, being lower.
(8 letters) I have -I---A-N
48 Across - "Longchamp favourite hurdling as racehorse"
(6 letters) I have C---E- "CHASER" possibly?
33 Down - "Sickly character called out for drink"
(5 and 3) I have -R-E- T-- "GREEN TEA"? The "TEA" part would possibly sound like "TEE" as in the character "T" but how would "GREEN" equate to "SICKLY"?