*puts on sensible head and thinks of her music teacher*
First of all, DON'T PANIC!

Secondly, you've got 22 days to practice, and as I basically live in the music department at school, I've heard lots of AS Level recitals or bits of them and I don't think you need to play for that long... do you? Or am I missing something (sorry if I am)
For the accompanist, can your instumental teacher do it? Or your course teacher? Our head of music accompanies about 90% of candidated, either because they want her to or because they don't have anyone else.
I see from your profile you're a clarinettist. Can you find some like minded people or some teachers to do a quartet with, like a small wind group? Or find an arrangement of a piece for a few clarinets? I'm not sure if you can just use a pianist to make an ensemble or not.
Hope this helps

(sorry if its rubbish)