Walk away

The group D is the Recreational Class directive, and yes going for Group D is a feasible option.

CE is a different matter. A magic box to 240 would not fix it, You would probably find yourself having to do a complete re-wire of the mains electrics. A replacement of a lot of non-ce equipment (e.g. VHF) plus the cost of the inspection.

IIRC it is illegal to sell on a boat in EU (purchased from outside EU) without CE but RYA can advise.