15 to 20 hours per year
VFR / Day only
Rents club aircraft or has a share in something relatively simple.
Sounds plausible.
The problem with averages is not knowing the standard deviation
The average of 0 and 10 is 5 allright but everybody knows it's meaningless.
Most surveys of GA that purport to show how many tens of thousands of active aircraft are there like to lump in everything right down to parachutes with lawn mowers on the back, but in reality 99% of those people rarely venture too far away from the hilltop off which they launched (I know, they do it where I live). I wouldn't call that "GA".
You can dig out license issue etc stats on the CAA website. We have discussed this here before. There isn't data on there to work out the active PPL population; possibly it is missing intentionally. One can have a go, by making some reasonable assumptions about the average age at which people get their PPL (which is on the website) and the age at which they either pack it in, or fail their medical. There is some extra info in the latest CAA survey of GA.
Renters are sure to fly few hours
on average - many do just the 12 min. I know a fair few that do close to zero; they need to fly with an examiner to renew every 2yrs. Group owners will be flying more. Outright owners will be flying the most; I do 150hrs/year and I know a fair few (who are not on the internet, BTW) that do 300+ hrs/year. Most IRs are owners. Most GA business flights are done by owners.
No matter how you look at it, there is a vast spread of activities which makes any generalisation hard.
Reading your posts elsewhere, you can build a supporting case for ultralights taking over GA and that may well happen but if it does it will kill off most GA airfields, which will confine flying to private strips, a bit like fishing going on from private fishing clubs with exclusive right for that lake and absolutely no new members unless vetted by the local masonic lodge. OK if you are into that sort of thing; very poor enroute visibility due to having one's nose buried up everybody else's back end