Does anyone remember those gross joints in Soho where they had booths with a view of a stripper in which you could toss yourself off in private if the fancy took you and you wanted to add to the slime on the floor? If that experience counts as punting, then I had a one-off around 1975 aged about 18 and then told my mates I'd see them in the pub after they'd had their self-gratification on subsequent visits to the West End.
As for a punt involving contact with someone else's skin, my first was around 1980 in a Soho walk-up when my then wife had health problems involving long hospital stays and during those I badly missed sex and, to be honest, just wanted some diversion and some company on my way home from hospital visits. The punt was with a charming mature French lady dressed in a purple basque (I say mature as that was how she struck me at the time: she was probably about 35). It was quite quaint: she began by asking me if it was my first time (which, of course, it wasn't, although I was probably coy about the details) and, after asking me to undress, she tenderly washed my bits and pieces with soap and water from an old-fashioned wash-basin on the dressing table that she filled up from a kettle. I don't really remember much about the sex, but it must have met my needs at the time as I went back a few times until my wife's health improved.
I'm not proud of punting because of my wife's unavailability due to ill health, but I can't imagine other men haven't done the same. As my wife had much the same social circle as me, seeking sexual solace with a friend would have been just as bad, if not worse, as regards my self-respect and a potential disaster area for relations with my wife.
Cheers!