Other than rest, what do people generally do? Should I work on technique-y things or learn other repertoire or what? Not sure if to keep practising my diploma pieces if I need to retake the recital!

No, don't keep practising the pieces! You'll go mad. Have about a week of doing nothing but fun, whatever-you-want-to-play practice sessions - not even practice sessions, just playing sessions, and then decide after that.

If you do have to retake (fingers crossed you won't, anyway!), your pieces will be much fresher if you've had a break from them. You might well want to do different pieces, anyway!

Sorry to hear you're negative about your recital. How was the rest of your exam? (sorry if you've said in another thread, I haven't seen it).

I was fairly happy with it all when I came out of the exam, but now I can really remember the glaring mistakes and wondering if that DipABRSM level it will cost me dearly. I am of course just rambling, but my teacher did say to me last night that I shouldn't worry about passing or failing, it's more about enjoying the performance opportunity etc, and once I was in there, the nerves did disappear. (stops trying to make herself feel better..)

Don't do anything. You can't retake until December anyway so why bore yourself stupid now? Also, it is tempting to try LRSM repertoire now but I wouldn't tempt fate either. The summer is here (allegedly) go out, get drunk and fall in love.

I've been havin a go at some Granados Spanish Dances to put me in the holiday mood. it's great to play something diffrent!!!