Hi, I have applied to study law next year at a NON-RG uni although my predicted grades would get me into somewhere that is a member. I would say the most important thing is to look at as many Unis as you can and base the majority of your decision on how you feel there. Talk to staff members, talk to students, have a good look around.
There are some good Non-RG universities for law such as, Kent, Sussex, UEA etc.