What are the chances of catching an STD during unprotected?

[Chiltern Line]

In the UK, the chances of contracting HIV from protected sex, if the condom is used properly, is indeed pretty low. But there are other things, notably gonorrhoea and Chlamydia, that are much, much more common, and can also be passed on via oral. Some cases of gonorrhoea are becoming resistant to antibiotics and can be tough to treat.

Also, I think your rationale about city vs country is severely flawed. Not only do people move about, but in metropolitan areas if anything they're more likely to be safe sex savvy.

Bottom line, never bareback an escort OR a civvy - the latter at least until you know them well/both go for a screen first.