What I would suggest, is actually having a balanced programme. Most people that I know of would take a four-part programme, barely cramming it into the 35 min recital. Of which it usually included:
1 baroque piece of short length
1 major classical sonata
1 light romantic piece
1 short 20th C piece.
I highly discourage you from playing two classical sonatas for DipABRSM, but instead adopt an all-rounded programme.
For me I did a three-part recital:
Bach - Toccata in E minor BWV 914
Beethoven - Pathetique Sonata
Bartok - 6 Dances in Bulgarian Rhythm