GCSEs, Latin or ClassicsWatch this thread
Latin would be better if you might want to do a classics degree later though (or similar ancient languages degree). Bear in mind also you can become a solicitor or barrister with any undergraduate degree, not just a law degree (something like 50% of solicitors currently practicing have a non-law degree for their UG degree). You don't even need to do a conversion course to become a solicitor anymore specifically, as all those wanting to become a solicitor have to sit the SQE regardless of first degree.
As noted in your other thread your GCSE subjects do not matter whatsoever in whatever you may later do as a career. Universities only care directly about your GCSEs grades, not what subjects they were in, and employers care even less about them. The only except is for certain core subjects (normally maths and English language) which often a minimum grade is required by both unis and employers.
Just pick whatever you think you'll get a good grade in and will enjoy studying. No university admissions tutor is going to waste their time umming and ahhing over whether an applicant did or didn't take a specific GCSE subject, especially for a course like law which has no prerequisites.
Out of Latin and Class Civ, that depends if you prefer history based subjects, or language based subjects. You know your own strengths and weaknesses, so play to that.
You have asked in this thread three times which GCSEs you should take. People have already said it doesn't matter. As long as you have English Language and Maths, the others are entirely up to you.