The Azores is part of Portugal, and therefore of the EU. It has concessionary low rate of VAT (8%??), and for that reason EU residents (other than Azorians) are not permitted to pay their VAT on imports there. You are obliged to wait until you reach mainland Europe.
That's what we were told when we passed through 3 years ago: the rules may have changed since.
If the boat was built and fitted out in UK then vat will have been paid at the time on most of the component parts.
Dover yacht unit ceased to exist many years ago despite info in vat booklet from Customs and excise
Try your local vat advice centre who were very helpful in my case with a bought hull and self finished boat. with good invoice records showing vat paid on major components they provided a "vat deemed paid letter" which has been used around europe.
The key thing is evidence that vat was paid in uk during build and fitting out which should be obtainable somehow.
Good luck, it's worth the effort.