technically this should say "some from the UK" as Great Britain is only England, Wales and Scotland and I think some of the people in Northern Ireland might get annoyed at it too.
Personally I don't really mind if it is considered a country but you are right, it is a collection of countries. Its like Africa being referred to as 1 country - it really isn't technically but a lot of people do for simplicity rather than calling it a continent. UK is I guess a kingdom but even wikipedia claims its a country -
https://en.wikipedia.org/wiki/United_Kingdom