You need to have a US PSN account but packs 1 & 2 are free at the moment (and compatible with the UK game) for anyone like moi who doesn't have them/haven't really played it yet!
Engine rebuilt by: Steve Horrocks & Andy Jones Engine mapped by: Ryan@2bartuning (330 bhp & 325 lbft @ 1.4 bar) Current Status: F****D