It depends on what "prospects" you're after, and what you want to gain personally from your time at university.
I'd say that, from your list, the 'best' university from an academic reputation point of view is probably King's, followed by Kent. I'd say that wherever you go, you'll find a diverse student mix both in terms of ethnicity and a whole hoard of other factors.
Not that any of this matters - if you think that any university will give you prospects without effort from yourself, you're heading for disappointment. University offers you the opportunity of good 'prospects', but you get out of it what you put in. Fancy putting in nothing? Then it's a waste of time going to uni and saddling yourself with debt. Fancy making the effort - go for it; have a look at the various unis and go with your gut feeling - you'll have to live there for the next three years!
Steve