"I want one thats totally original and in fairly mint condition and has low millage. Whats the price range?"
That sort of statement you looking at £5k+ really, especially is its low miles with HPI clear.
I sold mine for just under £6k 3 years ago, its was hpi clear, and nicely restored, but no way mint and had about 90k on the clock!
Best thing to do mate is to go to your local RSOC meet, normally once a month. and see if anyone has an S1 there, i think its very important to get fammiliar with the car before you go looking so you have a benchmark to work from.
Id also steer clear from ebay and infact most classifieds ads.
Last month i looked at getting another S1, and after 2 weeks of looking and spending nearly £100 on HPi checks, i gave up!!
The cars were either very over priced, or about £2 but turned out to be stolen recovereds or writeoffs
the sellers lied to me and also still seemed to think their cars were worth a fortune cos they are "rare".
The S1 is not a rare car, finding a nice clean example S1 is rare!
Best thing you can do is put up a wanted add, that way you get people coming to you, and these guys are generally the good ones who have nothing to hide or are not emabrrased buy the car. You get a few dodgy ones, but u can spot them a mile off as they are too keen and seem desperate!