I bought my liferaft. It's a PAL2 - a two person one make by Parmaris. It cost about £650 when I got it a couple of years ago and I think I got it from AFE although you might be able to get it direct - here's the link
http://www.inflatable-lifejackets.co...fejackets.html. It weights about 10kg, which in my C150 does cut down the amount of fuel available by about 3 gallons (just over half an hour's range), but I think it's well worth it. I don't like the thought of a single failure (the engine) causing me to end up bobbing around in the channel hoping that someone will find me before I die of hypothermia!
I'm not too sure where you can hire them from - but as incipientspin says, your flying club (or a flying club at one of the airfields close to the channel) would be a good starting place.
Thanks for the formula - I was close in a completely wrong sort of way
