Dweste, I am glad you got out of it OK and that the whole thing is now just an internet chat, but I am puzzled by a couple of things. You say your clothing was "doing its job" but shortly thereafter you were "shivering uncontrollably" I doubt your clothing was working very well. You would have been much better off in a wet suit. The best combination for sea kayaking that I have used is a farmer john topped with a float coat; the coat can be easily adjusted for exertion and is less cumbersome than a PFD. The better float coats are rated as PFDs (class III, I believe).

It is important to know the temperature of the water in which you will be paddling - there is a big difference between 55 and 65. I am surprised that your water temps might have been in the 60s at this time of year. In the Channel Islands, well to the south of you, we attain 60 degrees only in the late summer; water temps in the high 40s are pretty common during winter. At that point it is worth thinking about dry suits.

Again, glad you are back and talking about your experience. Thanks for sharing it with us - that way we can all learn.