Many law firms recruit university-blind.
No university will "give you" a job in a law firm. Law firms recruit on individual qualities, not on the basis of which university a person studied at.
I suggest that you study whichever subject that you are most interested in at a university which you think that you would enjoy being a member of.
If you are interested in English, the chance to study it in depth for three years may not come again. If you become a lawyer, you will have years or decades of looking at the law.
If you are interested in the law in its own right, then study law.
Each of Sheffield and Exeter is a well regarded university.
Good luck, whatever you decide.