I'm not taking the exam for a while yet (I skipped Grade 7 too), but I've been playing the Schubert, which is nice but you need big hands! It's hard to balance the different parts in the right hand, and to pedal correctly so that all those quavers in the left hand don't cloud things up!
Praeludium seems interesting, I do like 20th century repertoire very much - that one seems particularly hard because of the unusual time groupings of notes. The middle section is lovely though. I'm playing the Handel fugue myself, which I found deathly dull at first, but now I've had chance to absorb the music I think it's wonderful. I enjoy singing the different parts as I play along (bit of a Glenn Gould fan, y'see).
The Debussy I've only briefly looked at - it's quite humorous! And colourful

Your programme, although they are all good pieces, seems an unusual mix, as you have two modern pieces. Perhaps a Baroque piece from the A list or a Romantic piece from the C list would have created a more balanced programme, but this is not terribly important. You've set yourself quite a challenge with those pieces! When you practise listen as carefully as you can. Do the phrases flow? Are the chords balanced? Do you articulate well? Is the pedalling effective? There are endless amounts of things to work on at this level. Oh, and if you're not already, DO practise scales everyday. There are 150 of them for Grade 8, so learning them sooner will make the whole giant mammoth task easier. Plus it strengthens and improves the dexterity of your fingers.
Good luck with the exam!