You may also want to take a look at gliding for a bit.
Many clubs run a cadet scheme which gives very cheap or even free flying to solo - you should still be young enough. Post solo, it is still cheap (I pay 20p /min = £12 / hour + £4 for a launch by winch normally to about 1500' - a 2000' aerotow costs about £20 at most clubs).
There are also a lot of uni gliding clubs again offering cheap flying.
The hours won't count towards a PPL (except for the NPPL once you get a Glider Pilots License), but you may find it an affordable way of keeping flying until you are earning properly.
The downside is you will really need to commit to being on the airfield ALL day for a total of about 30 mins flying (4 - 6 flights)whilst learning.