It is against the law, anyway there are a raft of other charges that could be brought such as indecent exposure, outraging public decency and so on. It also contravenes local Public Health regulations.
A Police Officer may excercise discretion before bringing a charge, but that is entirely up to his or her judgement.
You can urinate in a field or hedgerow that does not form part of the highway, and coachmen may urinate up the nearside of the coach wheel!
It is a dirty, unpleasant and anti-social habit, to urinate in a busy city street should always result in a prosecution, there are other places where it is still illegal but might be considered less offensive such as a beach, or cliff top footpath etc.
I sometimes suffer from an "over active" bowel, does that mean I can poo in the street? I think that if you eat enough "beef" burgers you might be able to apply for a licence :roll:
H