Hi,
From what i've heard law is based at Collegiate Crescent, approximately a 5 to 10 minutes walk from most self catering halls.
I'll be doing a LLB/Matrise in English and French law, and the first year is at Sheffield hallam uni. Having never been to Sheffield before, i found myself in the same position as you, having absolutely no idea of which accommodation to choose. But I read some forum threads about halls that should be avoided etc, and got in touch with SHU's international accommodation services to have some advice, and I made my mind up quite easily thanks to their help.
So what I can basically tell you is avoid UNITE if you can as they are not a good value for money, still the Forge and The Anvil are good accommodations students said and are owned by UNITE. Sometimes you don't have much of a choice though, as you can guess the best halls run out of available rooms pretty quickly.
If there are any SHU law students reading this, could you please tell me about your first year timetable please? Merci beaucoup!