Hello! Which university of those mentioned are best for LLM in IHRL?

You're not looking at schools like LSE or Essex? The ones you mentioned aren't typically well known for human rights law.

If I had to rank them generically it would be:

Leeds
Sussex
Leicester

... but their IHRL programs aren't particularly notable. If you're not applying to other / better schools, I'd go with Leeds, unless one of the other programs stands out to you in terms of curriculum or faculty.