I would say that while reputation matters - and I agree that UCL and the Courtauld both carry more weight than UCSD in terms of international reputation - what really matters is where you can do what you want to do and where you can get the money to do it. In other words, in the long run what really matters is what you accomplish NOT where you go.
I did my MA in London. While it got me into the PhD program I'll be starting in the fall (leaning towards Berkeley), one of the reasons I didn't even apply to UK PhD programs is because of the funding and because they are only 3 years. In my mind, both of these factors were going to limit what I would potentially be able to accomplished.