I'm not at the stage of even considering applying to a masters course, but I'm curious to know how Oxbridge select applicants for their masters programmes. I emailed Oxbridge postgraduate admissions office asking if a students undergraduate university would affect their chances of receiving a postgraduate offer. They completely evaded my question, and gave their usual links to generic online FAQs. Does a student's undergraduate university, like its position in the league table / reputation determine postgraduate chances, all else being equal like grade, and personal statement?
I know someone doing a PhD at Oxford in Physics, having graduated from Royal Holloway. Anything is possible if you prove you're capable. Just find a way of proving that.
If you did consistently well, they will consider you.
I went via each institution's online application system, no UCAS fussing.
Is there any benefit/point to going through UCAS for postgrad?
In fact, I didn't even know that you could!
One of my high school teachers did her BSc at UEL, MSc at Exeter and PhD at Cambridge. Anything is possible.
The head of the Cambridge Group in their history department did his PhD at Cambridge, a master's at Oxford-- and a BA at the Open University.
Get good marks, good recommendations, and a reasonable proposal, and you have a fair chance.