I don't believe anyone who says they can't afford it; I got mine while I was studying for a PhD and earning about £8k a year.
Basically:
a) I rarely went out drinking and, if I did, I only had a couple.
b) Thank God for Tescos Value. Cheap pasta and tomato dinners with veg-various and meat on special occasions.
c) Got a part-time job for 10 hours a week during evenings and weekends.
This meant I could afford a lesson every week or two. I got my PPL in 18 months and around 55 hours.