Wonder if this is another one of those problems that is particular to UK GA flying?
Where I fly (Sweden), most people who start their PPL training in a flying club are in the 30 - 40 year bracket, since few will afford it before that... There are older beginners as well, but they are in a minority (they tend to go to soaring or ultralights instead). The younger ones tend to be the most active, so the people I come across at the club are generally in the 30 - 60 bracket; at 36 I'm rarely the youngest. Our flying school has been swamped with new students, signing up faster than we can train them, and it's been that way for several years.
"GA in Europe" is not the same as "GA in the UK"...