Welcome to UK-Y
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I don't know all that much about Human Resource Managment as a masters degree, but after a quick internet search, it seems that quite a few UK universities offer it as a postgraduate degree.
The problem in terms of fees is that it doesn't really matter whether you go to a top university like Oxford or Cambridge, or if you attend a less well-known school - the fees are all basically the same (give or take a couple of thousand dollars). A UK undergraduate student at Oxford will pay the same fees as an undergraduate at just about any other university in the country. Master's degrees are slightly different in that the course cost can vary by subject and university, but that doesn't necessarily mean that Oxford and Cambridge are the most expensive (for example, one top university may offer an MSc at $6,000 per year but another generally less good school may offer the same subject for $15,000 per year).
Unfortunately, as an international student you'll be looking at paying somewhere between $15,000-$30,000 for a 1-year masters degree and there's not really any way to get around this (unless you can get funding or a good US student loan). You can only qualify for home-student fees is if you've been living in the UK for at least 3 years prior to starting the course
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I hope this helps a little - good luck with your planning