Well, as they say, the aircraft has no idea it is over water so the aircraft will not be concerned.
I have crossed the channel in a lot less aircraft so I wouldnt worry about the aircraft being up to the job. I would take a liferaft, and I would make sure you are happy to fly on instruments or be careful about the conditions on the day as it can be VFR over the land and very poor VFR over the sea.
By all means take life jackets as well but should the worse come to the worse they will not do you much good by themselves at this time of year unless they pick you up in double quick time.