Subjects
I have no idea what your pilot was on about with the technical drawing...never heard such c**p.
Basically..be reasonably good at Maths & Physics. Not essential that you even pass your A levels in them cos A level standard actually goes beyond what you need to know for the maths (basic arithmetic, fomulas, and geometry )& physics in the flying exams. Some people will try telling you that you need geography..but you don't.
Also, far from essential, but a couple of languages wouldn't do you any harm..again, not needing to be fluent..just be able to waffle through a conversation now and then.
Good luck