A number of years ago 120 Sqdn at RAF Kinloss ran a weekend survival course for civilian pilots, mainly aimed at PPLs.
I don't recall hearing about this. I've been flying from Inverness since 1987.
I always wear a lifejacket, but my only non wet suit experience in winter was dinghy sailing in the 60s and canoeing till the mid 80s. The effect of being in cold water, wearing warm "ordinary" clothing, varies very much from person to person. I'm optimistic.