First of all, kudos for following your dream.
Second, law is not considered a "science". The typical science subjects are: maths, physics, biology, and chemistry.
If by some fluke they consider other science subjects, they can include: economics, psychology, geography, computer science, and sociology, before they consider law, business, and politics. See:
https://en.wikipedia.org/wiki/Branches_of_scienceWith veterinary science, it's a core science subject, so you would be looking at physics, biology, and chemistry mostly. Maths would come in at a close second, but you would need to check the entry requirements of the individual degree (their definitions can vary). Failing that, you would need to contact undergrad admissions to clarify their definitions
Even if you do take a Level 3 veterinary course, they might not accept you if the specific qualification isn't one that they accept (see their entry requirements). As veterinary science is one of the more competitive degrees (alongside dentistry and medicine), chances are they will be picky.
For foundation year courses, there is a chance that they might accept you. You will need to check the entry requirements of the individual degree though. See the following for example:
https://www.uclan.ac.uk/undergraduate/courses/veterinary-medicine-surgery-foundation-entry-bvms (any subjects)
https://www.nottingham.ac.uk/studywithus/ugstudy/courses/UG/Veterinary-Medicine-and-Surgery-including-a-Gateway-Year-BVM-BVS-with-BVMedSci-BVMBVS-U6UVTMGY.html (need both biology and chemistry)
https://www.bristol.ac.uk/study/undergraduate/2025/vet-science/bvsc-gateway-to-veterinary-science/#entry-requirements (biology or chemistry, so you are eligible if you meet the grade requirements)
https://www.rvc.ac.uk/study/undergraduate/veterinary-gateway#panel-a-levels (require chemistry)
I would recommend doing Chemistry A Level privately, if you can't find an adult college that offers it as an A Level for applicants older than 18 years old. You should also do the practical assessment with the A Level to maximise your chances of acceptance, but this will likely cost an extra £1000 on top of your exam fees.
If not, you are likely looking at Access to HE courses with strong biology and chemistry content (check the entry requirements of individual degrees before doing this) or do a foundation year.
If by some odd situation where they accept Maths instead of Chemistry, I would opt for Maths because you don't need to arrange to do the practical assessment. It's a complete pain to get it arrange. However, I don't think many unis that offer veterinary medicine would offer this.