No time to read all the comments except to emphatically agree this is 1. illegal (I would assume, in the UK, this very well meets a harassment or stalking definition, like it does here in the US), and 2. needs to be dealt with. Bluntly, this guy (you will of course not call him that) needs to get started on having that criminal record he so richly deserves.

Also, some video of him trying to force himself into your space might be useful, should it happen that you can be "holding your phone" with video running just in case he catches up to you while you are in transit on foot. I have found it very easy to take video without anyone realizing it with my phone right out in front of me as long as they don't see the screen, if I just act like I'm absent-mindedly holding it against my chest (not looking at it after being sure it's running, etc.). Be careful, of course. (Or heck...get a body cam / GoPro type camera. There is at least one app designed to stream video to another location during an incident but I have not read up on them in a year or two—worth investigating. A copy being created elsewhere at the same time could be useful if it's easy to make happen.)

This guy needs what's coming to him. All of them do who stalk and harass like this. Help him out. He wants a criminal record—give it to him if the avenue to do so safely presents itself. If he's going to follow women around, the fact that he does so should follow HIM around.