Damn... I live in Bristol!
We went on a Thames cruise early in Feb - I know one guy kept his boat on the Thames - can't remember his name though
Geoff as in www.boatlaunch.co.uk
lives near London he may be able to give you some more names of people in that neck of the woods.
Keep an eye open for people planning trips - I'm sure they wouldn't mind some extra crew
(Probably going to Southampton on Sunday