@Lady_Penelope @KeepTakingTheSoma @Ziltoidia @macha Yes, it was popular back in the day. I suspect increased regulation (H&S) on farmers and growers, and modern employment law killed it.
After WW2, in the austerity years, going on a working holiday with the kids to the fruit and hop-picking in the West Country and Cornwall was probably a relief from the inner city.

This article mentions the importance of the railways, so I'm guessing the Beecham cuts in 1963 also helped to end it.
https://www.whodoyouthinkyouaremagazine.com/feature/hop-picking-holidays