I know you know the guy at US Automotive? I think it is?
I have heard good things about the place but I am not 100% sure it is the cheapest route to a deal on parts.
Anyway. It is a long time since i bought any parts for an American car in the UK so I am probably out of touch.
I mainly shop on the US Ebay.
I have had great service from some of the online vendors there and their prices (even with postage and our customs bandits) are usually at least 30% cheaper than the UK prices if not 50%. So it is always worth seeing if you can find what you need by that means first. I have bought loads of bits recently for the Corvette from Ebay (had three parcels already and have three more on the way) and so far have still only spent £70 in total.
Money is money after all and these days it is in short supply.