That's an even more arbitrary way of filtering than going by rankings. Don't do that.
Go on the university rankings page, take the top 40 or so, eliminate anything you immediately don't like (e.g. that uni's in Slough, that's a small town uni and I know I want to be in a city), try to ignore reputation as much as you can because to be brutally honest it doesn't matter even remotely as much as you think it does unless your goal is investment banking. If that is your goal, you should already know what the target unis are and I don't know why you're bringing entry requirements into it.
You might well end up with your final 5 being Oxford, Imperial, UCL, Warwick, Durham. It's OK if it does, but you're shooting yourself in the foot if you refuse to even consider anything else - there are a lot of really good courses out there, whereas if you go blindly on reputation you might end up hating the uni.