CAI's from £200-£450 so depends on your budget really.
ITG, APR/VWR, FORGE Twintake and REVO are the more expensive ones and EVOMS, Nuespeed, AMD, Volant are less so. Have a look at the ITG and EVOMS, covers both ends (cost wise) and probably not a load of difference in their performance, both are good. ITG for
whoosh dish and EVOMS for a bit of
cha cha cha.
EDIT: Evoms CAI on eBay ATM, may go cheap. Don't know if its for your car or a K04 though, you'd have to ask as you can't tell from the picture.