Just bought 2 new iphone 5 s?

I'm selling my brand new in box my iphone 5's amd wanted to know would they work to sellers in the UK?

If they were unlocked, yes. If they were not unlocked, or you aren't sure, then it's hard to say - maybe they will work for voice & text but not data, maybe they won't work at all.

If you update your question to say which carrier you bought them from (or if they were unlocked and bought directly from Apple) you would get a better answer.