Applying for a first degree

I've been wanting to do law in the UK, however due to some personal problems I did not do very well in my GCSE (equivalent). This led to me not having the usual A levels qualifications.

I have done well in my LNAT (at least for the multiple choice, since essay is subjective), yet I have be rejected by UCL and KCL. I'm not placing too much hope in the other unis right now.

Thus, I don't know if I should get a first degree in a "less competitive" field and apply later for law with my first degree as a mature student.

What do you guys think about this? If anyone has similar experience I'll be more than happy to hear from u.