They are available new for £389 on ebay plus £10 brand plus p and p from rultland cycling. If you buy a second hand one it is unlikely to go cheaper than this , and it will proberably not have the updated front wheel quick-release system or improved seat clamp clamp.
I could be wrong, but if the bike is fitted with with a cespro shifer it will not have the updates on. This has a sram therefore it will feature them.
I bought one , from Rutland ,but there are alot on offer at the moment,around£400-£500,this seems to be the cheapest I could find by some way.