Top university wise, maybe it's not the best subject - but if you're dead set against History and you also know you will likely get a good grade in Sociology A-level, then I'd do it. At the end of the day getting A*A*A* at A-level in Eng Lit, Spanish and Sociology is better than doing something for the 'reputation' of the subject like a hard science, maths or History and getting A*A*C, for example.
If at uni you know you'll want to do humanities or social science then Sociology is a great pick. For some reason Law departments at uni do not want Law A-level, so either Sociology or Politics A-levels would be my recommendations.
If your sixth form doesn't have it as option though that could be an issue. What do they offer as A-level options?