I've got the same dilemma as a lot of posters here. Yes, I do wear a lifejacket and I have had a day of dunker training through a diving club. I've read the AIC on ditching, seen the stats and know that I still run a big risk of dying from hypothermia when I ditch in the Channel (which is my longest overwater crossing so far). But yet I do draw the line at the liferaft and immersion suit. Cost of purchase, cost of upkeep and the general awkwardness and unattractiveness are all factors in that decision. Have to admit I'm inclined to buy one of those Fastfind Plus PLBs someday, even though all my club aircraft do have an ELT.
Doesn't mean I'm curious though, and I've read the discussion with interest. I've seen (and actually worn) the survival suits that are worn by offshore workers when they are being ferried to/from the rigs, and they're thick rubber with attached, very stiff boots. I've also seen drysuits as worn by divers. But so far I have not seen/found a supplier of lightweight immersion suits used for general aviation. And I'm curious as to the stuff that the helo pilots use that ferry to the rigs. I mean, heaving to sweat it out for two hours every six weeks is allright, but what do you wear if you've got to fly in those conditions all day?