It has tape on the seatpost so almost certainly owned by a triathlete which means all the bolts on it will be over or under-tightened and it's probably been crashed a few times - probably into bridges while attached to the roof of an Audi.
It's going for a higher price than would have been the case before everybody starting hunting for classic geometry Cervelos in order to get 3cm legal. I would have guessed at £600-£700 being typical for a frame and fork a year ago.
On the subject of P3's, there's a shabby looking 54cm P3C on eBay currently at £824 with 10mins left. What am I missing here?...