The place to sell it is possibly on eBay, with a flag to the auction on here. A similar copy recently fetched seventy five quid there. No doubt someone will post a link to that thread.
How do you tell if it's a first edition by the way?
I'm sure mine must be, because I remember waiting for it to be published.
Thanks for the reply and advice - now stuck on ebay for what i think is a sensible asking price including postage for this mighty hardback.
You can also tell the edition via the ISBN number.