The trouble is, if I put it on eBay as a plain vanilla auction, like you said it could sell for £0.99, £99, or £299!   I don't particularly want to part with it for the former amount!!

A few months ago I looked at eBay's sold listings and I'm sure I saw a couple, albeit in the US, go for £2-300...

I don't think I'd want to part with it for less than about £100.  Is that too optimistic?!