I am inclined to say that you should study what you really wish to study, rather than a subject in which it might be easier to obtain a university place.
You could perhaps obtain offers to read law at QMUL, maybe QUB, RHUL, and a few other good places.
I suspect (but can't prove) that most people who do the PGDL chose their non-law degree because they were into its subject, and didn't wish to do a law degree, although maybe some are taking a strategic approach. I had no clue that I wanted to be a lawyer until the end of my second year reading history.
Pease bear in mind that law firms and barristers' chambers do not share the obsession with university rankings found on TSR, and some recruit university-blind. They recruit on the basis of individual qualities, not university brand names.
Good luck!