PS - the bit of the Molecatcher that I think really made my Mother make the threat was that in our family, it's not "sport", it's "frolicks". We tend to replace the rhyming word in the next line with "elbow" :-)

Later on, it "works out about tuppence a grind". There is a v. amusing thread somewhere about the effect of inflation on this song, and what the amount might be in today's money!

I've not heard anyone other than my folks do it so I don't know if that's the Bernard Wrigley version.