I went in 1979, just after we'd gone over to decimal coinage.
I still have a genuine 50p note, issued by the IOM mint.
It wins me pub bets time after time.....
We had the old and new English pound note circulating, the Irish one, the Manx one, and the the two Scottish ones, old and new.
After a while you just accepted any bit of green paper

It's not falling off, it's an upgrade opportunity.