11ft dinghy tender - help me understand tax and retrofit considerations

[Ifitsworthdoing]

Our forthcoming 34ft cruising catamaran (to be built in Poland starting later this year) we intend ordering a GRP dinghy tender of the OCT (NZ) or AST (Germany) type. This will be used in the UK for about a year prior to the arrival of the powerboat and our departure for retirement in the Med soon after.

Are dinghy tenders of less than 3.5 meters LOA affected by the VAT rules changes that are creating so much havoc on foot of Brexit? We intend taxing the powerboat (which will have its final outfit in the UK) in the EU under the '6 months UK stay then export' rule but are unsure whether it will be possible to do the same for the tender given that the dink will spend more than a year in the UK. If we tax it in the UK on arrival will it be likely taxed again later in the EU or are dinks exempt on account of their small size?

A supplemental question regarding retrofitting the tender with stuff like a seating bench & steering console as well as an American style T-Top sunroof/rain hood - both OCT and AST have told me that any such retrofits would invalidate the warranty and thus indirectly the CE certification of the tender. Any comments/experience on this from veteran boaters?