First of all, do you already have a degree?
UCAS (in case you don't know) is the Universities and Colleges Admissions Service. I applied for law school myself through them, though as an undergraduate.
I do not know how they evaluated my qualifications to their tariff or points system. I have a booklet that talks about their points system but it only mentions English, Welsh, or Scottish areas of skill (diploma, GCE, etc).
If you are applying and you have a diploma already, don't you just have to do a conversion course? Is that what you are doing? If so, I would talk directly to the firm or school. If they are really unhelpful I guess you could contact UCAS but if you are not applying through them, then I don't know what they can do. They may have some sort of thing where they convert your undergrad degree.
Sorry I can't be of much help as I am taking a different route. I will be going to Manchester University this fall and studying law as an undergrad, but if I can clarify any UCAS things, just let me know.
trisha