The OFFICal rule is you need the pass that belongs/fits to where that adress is-in your case UK. That would mean INterRail. In the past this was an advantage, as EUrail then was not even valid in UK.

That has all changed and there is no difference in price nor validity anymore-except that INt. is only valid MAX 2 days in home country.

Now UK does not give any hints in your passpt about visa etc-so you could also simply order EUrail and thus get even more travel rights also IN GB-noone will really care much.

As you read this it should be clear that all passes are also valid on the €*-but these need extra and high-cost REServ. on top and threse are currently now in such demand that they are hard to get-there is a set quota in each train for them-so advance planning etc is needed. Same-same for most hi-speed trains that about anyone here seems to want to use-mostly those in FRance. Forget that quick trip to Barcelona-fly there, much easier and cheaper too-go elsewhere by train.