Oh dear, I had hoped this thread would not degenerate into the worst of all our prejudices...
Seeing that the OP (who prefers St Andrews anyway over UCL) has scuttled off, one wonders if that was their intention all along.
Every single aspect of life is invariably "marmite" because we are intelligent and discern. That said, being a geek, from Eton and China (or an alternative equivalent of each of them) does not prevent some from being welcome and comfortable across the world, including Brixton (incidentally only 18 minutes by tube to UCL, acceptable travel to all reasonable beings) or Mayfair etc etc. I find that many cultures, even say where women are low status, education high/ low status, reverse snobbery etc etc is rife, will have no trouble accepting you as an individual if you actually see things from their world without renouncing your "tribe", and are clearly focussed on solutions and the possibilities of mutual betterment. The 'trouble' with tribe stability is that people fall for other members of the species, and anyway the best tribes adapt.
Often we choose to reject "marmite" when actually nobody is asking you to eat it, only to acknowledge others do and you're not there about "marmite" but a mutually beneficial "good". "Marmite" was never a problem when we had colonies supporting us, or when growth brought much easier living. A keen measure of how resilient and civilised one is is when things get tough. Few pass, so 48% may not be that bad.
Of course the less mature, regardless of age, and some with unstoppable egos, tend to default to the marmite judgement, perhaps even unconsciously. The loss is completely theirs. Turning away from places such as UCL is right for them, and much more importantly, a bonus for UCL and its students.
If you really cannot find a match for yourself socially and intellectually in London over 3 years, the problem is yours. Doesn't mean your time will be roses, however do you really expect much difference elsewhere? We all strive and learn, London is not the only place to do it, it may not be the right time when you're 18, but it works for a hell of a lot of people.