Both Peters, thanks for the useful comments. I'll take the 'survey' thing up again when winter is over.
With regard to Peter W's mention of the cost of launching, I have to say that I was quite shocked, while on holiday in the Purbeck area in July last year, at the cost of getting even my little boat afloat. The National Trust at Studland was as bad as the rest on a daily, or even weekly, basis. However they do an annual rate which, relatively speaking, works out quite reasonably, and their little boat park seems fairly secure: so I thought I would try keeping my boat there for the coming season and see how it works out. I must say I'm looking forward to NOT having to trailer to and from every single launch for a change!
Michael