the answer seems to be simple:
if you're looking to work with more mathematically minded students, and find maths the more interesting, warwick on balance is the place for you.
if you'd prefer to delve into economics further than maths, LSE is obviusly going to have a substantially better department for you.
personally i've gone with warwick, i'm looking forward to hitting the harder intake criteria. oh, and i don't really like the idea of going to uni in london.
i'm still waiting on a reply from bristol though...otherwise loughborough is my back up...