I am thinking much older. The UK fan base core is of folks who played when young, or their partners and offspring. As so few schools now play rugby, and this has been so since the 1990's, I would expect the average age of 'fans' in the UK to be in the high 50's.
It is why Wasps moved the qualifying age for the Senior tickets up by 5 years, because otherwise I would bet over half the ST holders would qualify.
I expect this to get 'worse' year by year.
If grass roots rugby cannot attract youngsters in sufficient numbers to offset the loss from schools, the game will die.