Just a couple of thoughts.
At anytime of year survival time in water is very short. A friend ditched in the channel a few years ago and was pulled out by helicopter in about 25 minutes. He tells me that you cannot believe how quickly the cold incapacitates you. He had a liferaft which failed to inflate!
My minimum equipment would be lifejackets(worn in readiness for the unexepected) and a life raft with rear seat passengers briefed to have it accessible and ready to remove from the aircraft in the unlikely event of ditching. Immersion suits would be brilliant if you consider the risk/cost worth it I personally wouldn't.
I have done the crossing direct numerous times. It is a calculated risk. To my mind in a well maintained aircraft and with suitable emergency equipment it is a small and acceptable risk.
I would echo internal_server_error's comments about talking to Jersey met and as far as routing I seem to recall I used to fly to ORTAC (on the FIR boundary mid - channel) and then direct to whichever island I was visiting.
Carry out thorough preparation and enjoy, it is worth the effort.
All the CIs are great as a destination.