Which is the best UG course for AI and ML etc

CS and/or maths. There's a lot of maths involved in those areas.

If you are considering data science at LSE I'm not sure why you aren't considering e.g. JMC at Imperial, CS at Oxbridge, etc. Those courses would probably be better than the LSE one anyway (as they focus a lot on the mathematical aspects of CS regardless).

Whether the degree has the term "artificial intelligence" in the degree name is irrelevant - what matters is the course content. You probably want a fairly mathematical CS degree in general (e.g. Oxbridge, Imperial, Edinburgh, Warwick, Bristol), and to consider a joint honours with a maths department with stats offerings if possible (e.g. Imperial, Oxford, many others).

Warwick data science or discrete maths might also be a consideration, as they have a fair bit of involvement of the CS department I believe? To be fair you can go into the field with just a maths degree (or even a physics or engineering degree) but may as well do the CS stuff in the degree if that's your aim.

That said by the time you graduate that bubble may have burst so you should be planning to do the degree for other reasons as well. "Tech" buzzwords often have limited shelf life. You need to be adaptable and be able to work in whatever is the flavour of the month and not pigeonhole yourself into something that may well be old news by the time you hit the job market.