Usully best to start looking on the following (i'm sure you already aware tho but just incase)
http://www.autotrader.co.ukhttp://www.pistonheads.co.uk Classifieds
http://www.ebay.co.ukLSD's for sale on ebay at the moment so if you cant find the right car with a LSD perhaps take in to account you could buy one for £500 and have one fitted.
http://cgi.ebay.co.uk/Ford-Racing-Puma- ... 35a3c43a70David