Hey Shellby,
They must be full then at Fareham, I applied just over a month ago and have my Stage 1 on 20th May at Fareham.
I kind of feel the same as you, my mental arithmetic is not that good so lots of practice I think!! I only left school with GCSE's and don't think that would necessarily make me any less capable. If you can prove yourself through the assessments then I think that is all that would matter.
Good luck!!!