Thanks for the responses, and sorry about posting in the wrong section.
I had looked on ebay but only had one result and that seller wasn't responding to email. However that was ebay AUS, not UK- and as your link shows there are a few seats available, although the biggest issue seems to be postage to Aus.
I'll follow up those links, but if anyone has one for sale 'privately' I'd be looking to spend between 50- 100 pounds depending on condition.
Cheers
Jon