Portugal makes registration complex. At the port captains office they STRONGLY advised me against registering.
Portugal requires at least an RYA day skipper or their own equivalent to register or use any MOTORIZED boat. This includes Aux.
diesel or
outboard.
They also require rather frequent pull-outs for registration and
inspection and they like to require re-liscensure at certain AGES, not your
boats...YOURS.
Poland does have a registration scheme which is a lifetime registration. I don't know if they require insurance but I can tell you, I could
NOT find a UK insurer who would
insure in either Poland or Portugal. The reason...Only Poland and Portugal, in the EU, require that the policy be written in their language.
Belgium no longer insures non-nationals.
Dutch "simple registrations" are NOT registrations but merely a document stating you are the owner. Some EU countries refuse to recognize the "simple registration", MOST notable among them...Portugal. The Dutch do (or did when I last checked) have a real registration process but it ain't
cheap.
Despite Brexit, the UK is still allowing Non-citizen (part 2 registrations). They have a fast track available, but as part of part 2 you must do a tonnage
survey. I don't know if they will continue allowing type 2 registrations after January 31, 2021.