I applied to Oxford for Maths and got rejected. I also applied to Bath, ICL and Warwick was sort of done on a whim. I got an offer from Warwick, looked at the prospectus, looked at the website, looked at the location, looked at the social life, looked at the campus. There are more societies at Warwick than any other uni too.
Came to the conclusion it is, for me, the best all-round university in the country for what I need. I rejected ICL and Bath as they have the same offer as Warwick and I'd prefer to go to Warwick.
But that's just me, and for Maths. And if you do take some Maths-type modules at Warwick you are likely to be in much better hands than LSE.
I strongly suggest you look at the Warwick Uni website in some depth before you seriously consider rejecting an offer, I would suggest it would be a mistake.