Insurance or not?

Hi everyone. I could really do with some advice here. Basically, at the mo, I have Computing A, Maths B, Business B. Although I really really really hope to boost my Maths grade up to an A this year, I'm not sure I will. So, I'm definitely going to accept Imperial as my firm choice, but my question is, do I choose UCL or King's as my insurance? How flexible are UCL in terms of results? I know they state that A in Mathematics is required, but would they still accept me if I did get a B? King's do not specify that the A has to be in Maths but I really don't wanna go there. Any help?