Thanks chezza and Steve although sadly in both links they only show the ‘speedfit’ plastic pipe fitting sort. I wanted to replace the stopcocks to my water softener in fact but I guess I’ll have to make do with the chrome/blue lever ones instead. 🙁
Have another look at the JG fitting.
They are used on copper pipe and are a push on fit.
I have used lots of these on water cooler installations and they are very good but must not be used on chrome plated pipe as the teeth in the fitting will not grip.