Really? I'm from the UK and I find "hey guys" and "you guys" to be quite common there. Maybe it's a generational thing - I'm sure it's something we picked up from the U.S..

The idea that it's sexist or problematic to address a mixed group as "guys" doesn't quite seem to have crossed the Atlantic yet, but I'm sure it's coming. The U.K. is never too far behind American cultural trends, especially the insane ones.