Who knows where I can find out about interpreting ornaments for Handel at Grade 8?

Theres a fairly good glossary in the ABRSM editions of the keyboard suites. Otherqise any good Baroque treatise will do. Do remember they are French Suites in style (English music at that time was greatly influenced by the music of France) so double dot where it is obvious. Otherwise look at the obvious, start trills from the upper notes, if there are any places crying out for ornamentation, put something sensible in.

Current fashion dictates that less is more. Both J C Bach and Joaquim Quantz are good places to start.