OAT and all other Commercial air training orgs. Don’t care, they may say there are minimum requirements but at the end of the day if you turn up with 60k or whatever, they aren’t going to say no.
There really isn't a massive amount of number crunching; most of the stuff is getting your head around concepts and memorising screeds of babble, most the thinking is in breaking down a problem into the component factors.
I don’t have the best academic results, no Higher maths (a bit easier than A-levels), a C at physics, never passed Higher English, but found the coarse just as challenging as those with a degree, its a steep learning curve for everyone, the main thing I found was having good study practices, it isn’t like school, no spoon feeding, nobody’s going to chase you up if you haven’t studied enough, you’ll simply fail.