I have a question for the expansive knowledge of the Forum!

I need to sell my existing bike, basically so I can order my new one. The main reason for selling the old one is that I just do not have room to store another bike. Sad I know, but sometimes that is how it has to be.
What I need to know is how much could I reasonably ask for my old bike? It is a 2008 Orange P7, 15″ frame and is in very good condition. It cost £800 new.

I’m not partuicularly tall or heavy so it hasn’t been hammered. The reason I’m getting a new one is that the Orange, although I like it has never felt quite right for me! Also I’ve had a little payout from work and I’m scratching the itch to spend some of it!

So what do you think, how much could I ask for?