If you are worried about numeracy then try out the psychometric test link I posted in the Interviews forum the other day.
The kind of numeracy skills you will need are somewhat different to typical ATPL equations and trig.
I tried the JP Morgan one which I imagine would be as challenging as you will get in an Airline. I found it pretty bloomin' hard and yet I find the ATPL maths trivial. No relation IMHO.
Give it a try.