Unless you apply to Cambridge then maths/physics are NOT required. What matters is that you take Bio, Chem and 2 other AS subjects that you feel confident you will attain an A in. Your grades,UKCAT/BMAT score, personal statement and performance at interview influence your chances of getting a place. Unless you take something like Critical Thinking then the other subjects you take bare very little significance.
Just passed my 1st year at UCL. UCL actually give a slight preference to those applicants who offer a "contrasting" subject at AS and/or A2 meaning the fact I took History to AS actually made them look on me slightly more favourably compared to an applicant with similar stats who had taken the cliche BIo,Chem, Maths,Physics.
So if you will enjoy and believe you have a higher chance of attaining an A in Socio more than Maths or Physics then go for it. It should not hinder your chances.