Exeter and Warwick are about the same, both good schools; rankings tell very little. Manchester's AAA is a straight up lie; they will take far below that but nevertheless a decent law school. Surrey's ABB is more realistic and a generally good school. If you are returning to your home country to work, do consider the international reputation of the schools. Manchester and Warwick are probably better known than Exeter and Surrey.
I would think about accommodation, scholarships, if you're international you might like students from the same country as you (think about the internationality of the student body), do think a lot about the type of city you want to live in. Exeter and Manchester are both cities; but Manchester is significantly larger. Do you want 50 McDonald's in Manchester or would you prefer Exeter's quaint restaurants vibe? Exeter has more of a community feel, campus and city-wide, whereas Manchester is another anonymous city. Manchester is a lovely place I wouldn't mind to live, though.
Also do consider to some extent course differences. One might be more essay-based and another more exam; if you prefer one over the other, you should decide accordingly. And to some extent course specialisms; Manchester, Warwick and Exeter have strong commercial specialists.