i think if your only going to get a D for maths, as i was (i "dropped* it, well more like kicked out
) , i would consider dropping it and taking another subject which you will get a better grade in, for example ABB in ICT Double and say Busniess would be better than say, CCD, in maths, physics and Chemistry.
I have chosen to take ICT Double and Physics because im good at them, and this way it will help be get a job in ICT in companies which i am planning on doing to fund my training. To be honest, i know pilots with no GCSE's or A-Levels... as long as you have a decent knowledge of Maths and Physics for the ATPL exams you should be fine, A-Levels will just improve your chances of landing a job. So, study subjects your good at, not what you think airlines want.
Your in a similar situation to me, apart from you have more grades. I will be living with my parents as well and i too wont mind the debt (i say that now but i dont know in a few years lol).