I have to agree please don't even think about going to quick fit???if you can't afford to have the mod done properly my advise is start saving and get it done right when you have the cash
I think it may be worth the trouble of waiting and getting into one of the specialists the guys on here recommend,do a search this topic as come up many times before,good luck.
I think tvrfix.com can do it for around £100. They know their TVRs and doubt an apprentice would "take it on a run to check the exhaust is fitted properly" (read as sneak off to thrash a cold engine and possibly write off your pride and joy) unlike a Kwik Fit chav.