Best mobile network to download t-o-r-r-e-n-t-s on? (Metaled)

This could either be 'gigabags' 'dongles' or regular sim top-ups/tarrifs. I'll start by saying this is a theoretic question so as to not suggest intent to break any copyright film laws. Giffgaff offer 6GB to use as you like (a film is roughly 1 GB) includ..