This might be a bit late, but if you still have questions about the UK system I could try to help. I'm a British student, and have accepted an offer for the Masters program at Oxford 2011/12. I also got an offer from the Courtauld but decided not to accept in the end.
I don't know about the league tables but the general reputation of Goldsmiths is nowhere near Oxbridge/Courtauld/UCL and some of the other places mentioned. The HoA department at Oxford is relatively young, but there have been art historians there for much longer. It is growing rapidly and has excellent library resources, galleries (Ashmolean) etc. Cambridge is more established, but only offer MPhil (research based) and PhD grad programs, rather than the 'taught MA with dissertation' model used elsewhere. The Courtauld tops them both in the league tables, but only just, and of course lots of other factors at play.
EDIT: disregarding the league tables, my opinion (and that of my professor, with whom I discussed this) is that Oxbridge and Courtauld are the only schools in the UK you should consider. I would consider UCL only as a back up option, unless a professor there really suited my interests, and Glasgow wouldn't even be on my list. Again, these are just the general perceptions of those in the UK. I've noticed that UCL has a better reputation in the US than it does within the UK, however, so it depends on who you want to impress.