Peter S, Thanks. I have indeed contacted Ampair. They would have been delighted to have sold me a new one but it is not currently within my budget and they had no knowledge of anything second hand. However, I think that I may write to them. I missed out on one on Ebay recently but that was my fault for not being bold enough. However, it is not needed this year,so I have time to keep looking.
Peter M, As it happens I do still have a key for Preston Marina ... so ...