Assuming you start now, you won't be able to get your PPL until you are 17. A three year PPL is unlikely to come in at 50 hours, probably more like 60, possibly even more. But then the cost is very spread out so it's not like you need £10k tomorrow.
There are plenty of scholarships available through GAPAN, or the air cadets, some for 12 hours which really gets you on your way and possibly even close to solo.