I literally...had worse results...and was doing engineering at Exeter...?
There are exactly three universities that offer engineering who give one jot about your GCSEs: Oxbridge and Imperial. This leaves at most 2 of your 5 applications in UCAS looking your GCSE performance.
It's irrelevant, y'all need to stop pretending like it isn't.
As for the US...are you a US citizen whose parents also have a large chunk of money saved up? If you're not a US citizen, are your parents mega rich (I mean, oil baron rich. Not "NHS consultant" rich)? Or, are you an Olympic level athlete? If the answer to more than one of those questions is no, it's not an option, as the only way you could afford to study there would be to get into Harvard (or maybe Princeton/Yale) which will cover your costs in one way or another, or getting an NCAA scholarship somewhere (which will probably be a mid-tier at best state school, if you don't get into Stanford/Berkeley).