They are expecting a balanced programme. If you have Bach, Beethoven, Chopin and Debussy in your programme, I think yours is a balanced one. Also, you may consider off-syllabus Chopin pieces of similar level of difficulty (if my memory serves me correctly, ABRSM needs not obtain prior approval, unlike Trinity). Please check the exam guidelines.Just curious, which C minor sonata of Beethoven are you going to play? No 5 or No 8? Or No 32 (off DipABRSM syllabus but on FRSM syllabus)? BTW, you should also note that long repeats should be avoided. Therefore, watch out for the min. playing time requirement.There is no rule, and you need not play in the sequence of periods. Some teachers suggest to play the piece of which the candidate has most confidence. Some teachers suggest to play the piece with a sonorous ending.Good luck!
Regarding the Chopin Waltz, which one did you have in mind? If you are talking about 34/2, that's graded at 7 on www.pianosyllabus.com whereas the Nocturne is graded at 10. That seems like it might be a problem - can you get these things pre-approved?