For very wealthy families (who can pay 3-4 times what it costs in the UK out of pocket), absolute star students (ie an Oxbridge offer would be fully expected) or world class athletes the US is worth considering. For most others it is going to be difficult to find an affordable option that is better than your U.K. choices. And you’ll have to spend a lot of money and time just to apply.
That being said, here’s a lengthy thread from a British student who went through this two years ago. Note that she was from a wealthy family and would have easily got into Oxbridge, but she still turned down Stanford (at a cost of $300K) for a scholarship at a college you’ve probably never heard of.