One easy answer, which is too limiting, is the Russell group.
A more helpful answer is to think what you enjoy doing that employers will value, and find a course that matches.
But be careful: what makes you think employers value an MSc? When I was doing a lot of interviewing for r&D positions, we came to the conclusion that there was only one valid reason to do a PhD: because you want to. In other words, a PhD did not make you more employable.
Having said that, I have seen a one year MSc conversion course turn a biochemist into a very competent EE. But the circumstances were unusual!
Before the usual chorus pipes up first degrees are highly beneficial.