check out minitorque.com for performance related info on the mini

all the below have more info on there
for me:
1. 15%/17% pulley plugs belt (KMT pulley ask 'Fisher' on here to help you out)
2. coilovers (KWs, FK, AP or better if you have the budget)
3. polybushings (superflex)
4. Janspeed manifold
5.
JCW GP or GRS intercooler
6. Newman Camshaft, 550 injectors and Mynes tune
7. dave.f hybrid airbox.
8. lightweight wheels and non runflat tyres (OZs + toyo t1rs are pretty good combo)
9. R56
JCW brembo brake kit
10. reduce weight of car / styling stuff