3 layers of cotton under garments, 1 waterproof rubber flying suit, a lifejacket (inflatable type), radio if waterproof or in a sealable pastic bag. Make sure you fly exactly the way you say you will on the flight plan. Tell someone you know to make sure you get where you're going at the time you say you will. Also take a small nose clip. A lot of deaths from immersion in cold water comes from the shock on entry, especially when inhaled etc.
Have a small liferaft in the back. Also fit floats! LOL
I personally wouldn't fly over water that far in an ill equipped R44, I have enough trouble doing it in an offshore equipped S76 but I have to feed my child somehow!
Hope you make it and have a good day out! Let us know what you do decide to do.
Oh yes, forgot, do a dunker course. You'll just love that!