If he could, I'd be doubtful South Korea would want him. Looking at some work visa requirements [1] they'd need a sponsoring company in South Korea. If they're working remotely for an English company it sounds like SK would say "Cool, keep working over there then".

If OP wants to live in SK with his fiance and work remotely for somewhere else, they'd probably be better off being a "tourist" and getting married and getting a SK visa that way. Yes, they're engaged because they didn't want to rush into that, but lots of people from different countries end up getting married in a hurry for this reason.

https://www.justlanded.com/english/South-Korea/South-Korea-G...

I hadn't given visa requirements much consideration, so good shout! Thanks.

I'm going to talk to my boss tomorrow but I think its unlikely, Korea is GMT+9. I'd have to work outside of normal GMT+0 hours. My boss is great, but something like this will require higher clearance, which I doubt I'll get.

If you work in times relative to Korea’s solar day, yes. You could conceivably work from 9-5 in GMT still (from 6PM-2AM local time).

I’m not saying it’s ideal, but you’re trying to pick the least bad of some dreadful options (for which I’m sorry and wish your fiancée [and you] well as you navigate this). Keeping your current job, working it as a “second shift” job from Korea might give you stability that’s valuable here.