Actually, I am 100% sure that Romania IS NOT Schengen. And the UK is also not Schengen. https://en.wikipedia.org/wiki/Schengen_Area

I nearly f. this up when I was traveling with my Non-EU girlfriend who was on a single entry Visa and I was about to book a flight for us from Vienna to Sofia to travel in East Europe.

The question is: Can citizens of Bulgaria and Romania just move to the UK without further requirements? Looks to me they would need a visa.