Not sure you'll get a lot of takers at that price Luke considering the spec and condition. I think £200-250 is more realistic. £500 buys a lot of bike these days considering that there are Revells 450r's and Transition Trail-or-parks in the buy sell section at that money.
Get the shocks serviced, the brakes bled and rotor sorted and some higher quality finishing gear and you might be knocking on the door of £350.
My Trek Jack 2 (http://www.pinkbike.com/photo/2800152/) sold for £300 this year and that was in perfect condition and of a very similar spec and took a long while to sell at that price.
Other than that- what sort of ballpark price were you looking for?