If you want to study medicine, HL Biology and HL Chemistry are a must. I assume you're applying for UK universities from EU (Finland)? In that case HL subjects are considered proper A levels with SL subjects being compared to AS grades, so you might need either HL Chemistry, or HL Chemistry and HL Biology depending on the university you're applying to.
For Oxbridge applications, however, I'd suggest avoiding Maths Studies completely (I don't think they consider your application if you take Maths Studies) and avoiding SL Maths if possible (though not entirely necessary). HL Maths may be a requirement, but if not will almost certainly offer a good advantage. Take Further Maths if given the opportunity (either school-taught or self-study) - it helps!
For Law, the requirements vary but I'd think English A is a requirement. Philosophy and psychology may definitely seem interesting, but will not help your application much (if at all) - perhaps it could instead help with your personal statement writing? Hope this helps!