Sort of, their payment site can convert USD to pounds. I just bought a set of TB armor from them no problem. As long as you have a credit/debit card you should be fine.
Just my opinion.
The armor changed in these films because of production reasons, not intentional timeline reasons.
Not to mention that most people are not as concerned with continuity as we all are. Thor has a different costume in every movie but it’s “supposed” to be the same outfit.
The red label scout helmet has a lined fiberglass dome so quite a bit heavier than ABS. It’s up to you ultimately but I know I would rather pay the extra £150 and not have a sore neck.
As for kits can’t go wrong with either TM or RS. RS is the most accurate to the films as they cast off an original suit, TM is a cleaned up version but still very accurate (I am amazed at how close Paul got without access to the LFL archives).
Definitely looks like R1 to me. Heck, wouldn't be surprised if those were Black Series helmets.
As for continuity, I think the “idea” is that there was ever only one TK armor. Even though we know better.