I’ve dug around the community forum, and you should reset the Hub to change the owner’s account.
You can register a UK account on Samsung’s UK website.
Actually there isn’t any way to transfer the ownership of a Hub between Samsung accounts. There was a single occasion where someone had mixed up devices on different shards, and ended up somehow transferring the ownership of some devices on one of the shards to a shared member. But obviously it is not a way.
I remembered that occasion regarding the ownership change, so please excuse me, if my comment was misleading.
Unfortunately, your Samsung account’s country cannot be changed from the Settings page. Samsung support can change it, but your account would be wiped out as well.
Some other manufacturers like Sonos has similar regional limitations. If you have a Google Home device and you want to add a Sonos speaker to it, you cannot add it if your Sonos account is not in one of the supported countries. But Sonos support is not hiding it. They even give advice, what they have from feedbacks from other users, to just change your Sonos account’s country. And it works well. And of course changing the account’s country is only takes that much time, as just finding where is that setting on the Sonos website. And meanwhile you can realise how much information is Sonos storing regarding your device. It is amazing how they visualise when you used your speaker during the past weeks or months. But suddenly, Samsung is completely different. And it is more like a pain here.