I avoid teens whenever possible and all I could add would be conjecture, we get enough of that.
Personal experience isn't conjecture. For example I see on a daily basis underage smoking and am often asked for a cigarette or if I will buy them for underage people. I live in London but on the outskirts now, not in the middle. I very rarely see underage people vaping. Can't remember the last time I did. I do see kids smoking dope, drinking and sniffing laughing gas from balloons. Regularly.
Every time I see I new vape shop appear I will go in for a look and (try to) converse with staff. I always ask about 'non smoker vapers', ie 'How many of your customers have never smoked prior to vaping?'' The last place I asked she said five. How many of that five use nic?
One. That would be adults, or at least of legal age to buy vape products which is 18 and over. Her reply would be about the average.
I see no evidence of any underage epidemic, or non smokers taking up vaping epidemic where I live and the places I frequent. I ride around a fair bit on my bike.
Non of that is very scientific but neither is the news articles we are reading or even some of the ''studies'' done by ''researchers''.