I've just done a quick search on ebay and has it happens theres one for sale that finishes in a couple of days , it might be worth keeping your eye on the auction ,to see what it fetches , on the ebay search page i just typed in "sanyo z1" , its currently at 180.00 but the current high bidder has only 1 feedback , but see what it sells for.
I reckon you should be able to get at least £250 for it.
I recently sold a 5-year-old old 800x600 video/data projector (Sharp NV4) for £260.
I think the key is to start the bidding low and pay the £9.99 to add it to the featured gallery. It seemed to get a lot more views than other similar models and sold for a lot more. I think a detailed description also helps.