Well in fact I'm in the most selective french scientific scholar section, I only can inform you on that,
and what i can tell you is that we got student from litterally all across the globe (Brazil, Japan, Maroc, Tunisia, Korea, Eastern Europe...) integrated in our classes.... some don't even speak good french (they've got extra courses to fill the gap)
They sent their files, if you're good enough, you're taken, and then
you come study, the only thing you gotta pay is like 75eur for photocopying, no extra charges, for anyone, even foreigners....
After 2 years like that, you pass some exams for different Engineer Schools and most of 'em, especially the most renowned, are free (or nearly free) and they welcome foreigners without extra charges too I guarantee that, some even got special foreigners-oriented entry exams (french doesn't count)....
It could be an option, but I totally understand that you wanna stay in UK.