stay at LSE (econ) or go to warwick (maths)

I'm a BSc Economics student at LSE I got a top performance in first year with 88% first year average, I have an offer for Imperial maths but conditional on STEP and I'm unsure if I will achieve that, I also have an unconditional from Warwick for maths which I have made my insurance choice.
So as a result I'm thinking of a back up plan if STEP doesn't swing my way; should I go to Warwick for maths or stay at LSE and switch to maths and econ given my good grades?
My goal atm (not sure if it's a good goal?) is to get onto Cambridge Part III maths, I am autistic and therefore have no interest in IB or finance or any of the usual grad scheme stuff other people do, only maths at the moment. I don't even want a traditional job at the end, I am really stuck in my ways due to how my brain works. (I'm nearly 20 years old and never even had a part time job lol, never done any extracurriculars or volunteering or whatever either, so on my CV it would only be grades lol). I would literally need to be top 1 at LSE to get onto part III if I stay whereas if I went to warwick I'd still need to do good but would be a lot better as its a much more rigorous maths course.
I just feel there is nothing for me at LSE especially since I don't like the people there especially because everyones obsessed with finance and haven't even spoken to a single person in first year so I feel like an alien or ghost.
So what should I do, what do you guys think?