I hope this won't sound blunt, it's just a bit of a heads up really.
First off as said, get a class one medical done at Gatwick.
Next, I would try to find a friendly instructor (or otherwise) who can go through some of the more mathematical stuff that may be required both in flight and for the ground exams. I apologise if this sounds patronising but I don't understand much about dyscalculia and this was a thought that came to mind.
In no way do you have to be a genius or straight A student to do so, but depending on ability, it may be quite tough. On the practical side it shouldn't be too bad, there is some fairly basic stuff involving 3 and 6 times tables etc. On the theoretical side, for the ATPL exams there are a couple of subjects (mainly General Navigation) which do require some trigonometry and manipulation of formula and numbers.
I just think it would be a good idea to get a good idea of what lies ahead. If you can't find someone to go through this stuff with you (maybe some discussion involving your strengths and weaknesses and maybe some examples of whats involved) I would suggest getting in touch with Bristol Ground school. They are a provider for the ATPL theory course in distance learning form, and I found them a top bunch of people when I was there and they might be able to advise a bit (One of their instructors, Tony Pike (IIRC) teaches G Nav and was extremely helpful to some students while I was there). You can find their details at
Bristol Groundschool | Leading EASA ATPL Distance Learning Specialist