Mathematics at the university of Warwick

That's quite harsh. Though I agree with your first paragraph, but a lot of people overseas do not know this (that is to say if the OP isn't currently studying in UK).

Keep it civilized, guys

OP - you should be able to find the answer to most of your questions from the links provided already.

If anything's unclear, post back

Nope, I'd go for the easiest option which is grade- AAA and S in step.

or apply to UCL or IMPERIAL which have lower requirements

Nope, I'd go for the easiest option which is grade- AAA and S in step.

I know the offers are A*A*A and 2 in step or A*AA and 1 in step. But I think I'm likely to get A*A*B and aim for a 1 in step by any chance would they still give me a place at Warwick?

I doubt it, the people I knew who missed the offer hadn't got the STEP grade, but had made their A-Levels. Like ttoby just said, you can't compensate by losing an A-Level grade here and doing better on STEP, it doesn't really work like that. If anything, I'd say make sure your A-Levels are good and that should take precedence over STEP, both for getting into Warwick (or possibly your insurance) and applying for jobs later - employers ask for your A-Levels but won't know about STEP.

Thanks for the help I am aiming to meet the requirements. Just wanting to know if something like that occurred if there was still a possibility to make it.