One doesn't "justify" it, one just does it.
There is cost but usually it's a matter of substitution - where I live cars are very expensive (200%+ duty!) It meant that I could fly and buy my own airplane for less thsn the cost of a new RAV4 every three years. I made that choice and choose to fly and have and old car - one added bonus was that I own the only four place fixed gear, fixed prop airplane available for rent in the country and so even with low rental levels I have found that my personal flying nets out at less thsn it costs me to drive to the airport.
The circumstances are unusual but overall it has cost a lot less than I expected.
In your situation if you can manage it I would borrow the money on a five year loan and get the PPL done quickly, then pay the loan on the drip for the next five years. If you have suppporting parents even bolt it on to their mortgage as suggested by another contributor (I assume at you age you don't have a mortgage of hour own), also there are some clever means of intetest free loans via credit cards if you know what you're doing (see moneysavingexpert.com).
It's never going to be cheap to fly but a group around a small permit type airplane should keep the cost down once you have the PPL.
Your GBP130 is a little under three times the price at Sothend about thirty years ago, so overall in "real" terms probably about the same. Seeing what match tickets and train fares are in the UK these days, a flying habit looks like a bargain compared to folloeing a football team - so if you want to fly and can scape the cash together do it.
One further 'justification', when you next apply for a job put flying on your CV and it'll make you stand out from the crowd - so it may have career/income boostingbenefits.
Good luck with it, you'll never regret it - airports the world over have car parks full of old men wistfully watching the airplanes and thinking "if only".