Those numbers for non contextual U.K. numbers for Durham are shocking and are probably replicated at most other unis that consider themselves recipients of those that don't get into Oxbridge. (St Andrew's, Edinburgh, Bristol, UCL, LSE, Kings, Warwick, Exeter etc).
My DC spent a year abroad in the USA as part of his degree. I wish we'd looked into it when he was considering where to go, instead of the U.K., as there are a lot of opportunities for help with funding. The quality of teaching was outstanding, the choice of modules and subjects huge (he actually got an education!), the pastoral care was incredible - he had more contact with tutors and profs in an academic year than the whole of the 2 years at the U.K. uni he attended, they had to go to lectures and seminars - participation and attendance counted towards final marks, the opportunities from an extra curricular point of view were unbelievable and really inclusive and welcoming. Because of the legal age for drinking it was not central to the culture of the place.
These US unis (not just the big names) are so well endowed (and supported by their alumni) that the funding and facilities cannot be compared to the U.K. - it was an eye opening experience and makes you realise students in the U.K. mainly pay £9250 plus living costs for a library card (and for the past several years teaching has been severely disrupted by strikes and some unis still persist with online). He realised how poor the academic experience is in the U.K. compared to the US.
So the fact we are losing a growing number of well qualified, academic kids abroad for their degrees as they get squeezed out of the U.K. system is a loss to our country. If it became more public what funding options there are to help people, and more support with applications etc, I'm sure many more would go!
This problem will get worse in the coming years as political pressure increases on unis and demographics mean U.K. cohort sizes increase (before decreasing again).