There is zero adult games discoverability in the UK. Unless I specifically know what I'm looking for, either because a friend mentioned it or because it's one of my own projects, it's just invisible to people in the UK most of the time.
I explicitly have a credit card so that I can prove my identity and access the game that I already uploaded to Steam on an account that is more than 18 years old. Deadass, I have this stupid, credit-decreasing chunk of plastic and all I've used it for is to buy snacks (To activate it) and so that Steam lets me view my own work. Joke country.