By half A Level I presume you mean AS levels, i.e. the first year of the full course?
Let me just try to clear a few things up:
PPL - you can fly, but not for financial gain. i.e. you can't get paid.
In order to be a paid flight instructor you will therefore need a Commercial Pilot Licence (CPL), with an instructor rating bolted on top.
Seeing as gaining a CPL requires ground exams which are around about the difficulty of GCSE, perhaps as far as AS, you need to think about whether or not you have the motivation to complete those.
Then we'll add in the costs. To finish your PPL (assuming the 30 hours you have are PUT, and that you haven't done any of the ground exams, and that you will finish the course in the 45) you should probably budget about £3k.
You'd then need to get to 150hrs TT (£10k), before taking your CPL (£5k) and your FI course (£4k). Before I get shouted at by other posters, these numbers are approximate figures, it can be done in less if you're clever about it.
In terms of funding, you would be better off getting a job. You won't get a loan without a job, you won't pay it back without a job, and why pay interest on something when you could just earn and save. (Personal Opinion).
All of this is around the forums. Please learn to use the search function.