Tip culture in the UK is very different.
Bang on. The usual in a pub is saying “One for yourself?” with your voice rising on the last syllable. If they accept, they’ll add the price of a drink. If not, no harm, no foul. Or drop some change into the charity jar - most pubs have one.
Sit down restaurants, if they don’t automatically include a service charge, you just round up to the nearest note value. Same with cabs and take away delivery drivers. If your bill is £12.20, you say “Call it £15.”
Tipping in the USA is a minefield for Brits, just like tipping in the UK is problematic for Americans. Different expectations. *shrug*
I’m Black and work in food service, its true that black people don’t tip as much but its usually something. I cringe whenever I hear a European accent knowing I’m not getting a tip at all. Arabs are the same but on occasion they tip big