I've not yet made a final decision but it looks like Volume 3 - Sea Kayak with Gordon Brown will be shot on the tapeless Canon XF300.
Prices online vary between £4,200 and £5,300 but a UK guarantee and prompt service is essential in a piece of kit like this. So I'll go fishing for some quotes.
Three other cameras I considered were the Panasonic AF101, the Sony FS100, and a camera I've used a lot on BBC jobs, the excellent Sony EX1.
Naturally, I've picked the most expensive of the bunch! But it's the best suited to my way of working, and the only one which conforms to the BBC's minimum requirements for HD production.