Can I do Law?

You can get into solid Russell groups with BBB grades but you will receive a AAA offer. It's all posturing and because of the abolition of caps concerning student numbers and the ABB requirement it's a buyers market. I wouldn't worry

That's a bit misleading since it is not common at all if you are talking about AAA RG courses.
A friend from my college who applied to Newcastle (which is just an average RG university) narrowly missed his AAA offer by getting AAB and got rejected straight away, even though they actually went into clearing.

Well Sheffield this year and last accepted people with BBB, as did QMUL and other universities I haven't heard about. Once you get the offer and have done a good personal statement they can often take you. However it obviously Dosent apply to all of them, as seen with Newcastle and Birmingham uni.

I thought of Sheffield as a good university before they gave an unconditional to someone who had CDDU at AS and no prospects of improving at A2 whatsoever, but it is incredibly unpredictable so I wouldn't advise OP to count on it.

I think the main point of Information that op needs to take away is that it is possible to get into a solid Russell group (other than Liverpool) with those grades, and Dosent need to lower their gaze to Lancaster or Leicester or wherever. Sheffield is a very solid school with good prospects for graduates and you will find lawyers in most top firms from Sheffield. Many students opt to stay around the region post graduation though or become barristers, and this does affect the numbers seen in city firms. Then again, I will agree that Sheffield probably isn't one of the universities where students are really concerned about their careers compared to places like Manchester and Warwick who have top notch law societies which arrange events with firms and commercial awareness societies