The obvious question is whether to start in the UK intending to transfer, or take another gap year.
Generally speaking the chances of getting accepted to a “top 50” university in the US as a freshman are usually higher than the chances of getting accepted as a transfer student. However, the number of international transfer students that come to the US is small enough to make it hard to say how possible it is other than “possible but tough”.
One thing that has occurred to me is that the Canadian education system is quite similar to the US system except for two big differences: The price of university is generally lower; and, Admissions is more predictable and more based on academics. One option then would be to start in the UK and apply to transfer to both some top 50 universities in the US and also a few of the top Canadian universities (Toronto, McGill, UBC). Then you can see where you get in.