I had the same problem. The phone was bought for me as a Christmas gift so I can't be sure it was originally from the UK. The initial language setup was German, so I'd guess not . I did the first setup without a sim installed. Anyway I was able to resolve the problem by putting in my UK sim and then doing a full factory reset. I also made sure not to install Android Pay second time round just in case, although that probably has nothing to do with it. After the reset the default language was UK and I was able to set up Samsung Pay without any issues. Hope this helps someone.
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