It all sounds very complicated!
By the sounds of it you'd be easier moving to the Channel Islands!
Depending on the size of your business could you not make Guernsey/Jersey a registered office of your company and have that purchase the rib thus by passing VAT?? There are also other benefits to having a business registered in the Channel Islands.....like a flat rate of 20% income tax!?
I'd assume the rib would have to stay here for a length of time before you could take it back to the UK (I assume...although could be wrong that it would follow similar rules to cars!?!?)?
However a lot of hassle for a boat!