I was in the last couple of years of primary school in 1971 so had to learn both systems Even as kids we realised that there was a huge increase in the cost of everyday items and a lot of confusion. I was living in Northern Ireland and 5 or 6 years later I was working part time in the "amusements" industry repairing the new electronic video machines etc. The Irish Punt was very devalued compared to the pound and the industry had terrible trouble with people using the dimensionally identical southern Irish coins in machines. At one point we shut all the automatic change machines because people were crosing the border with bags of 50p (1/2 Punt) coins feeding the machines, taking the 10p sterling coins back and exchanging them for Punts.
I got caught out returning from Ireland on the British Rail ferry in 1971, when I bought a cuppa onboard & got some Irish coins in my change.
Not noticing, I tucked them away in my wallet.
On arriving back in the UK, I had to pay for a train ticket, so I dug around in my somewhat diminished cash & presented the, (to my eye), correct amount.
The reaction was "You can't do that there 'ere," as the ticket bloke brandished the offending Irish coin.
Tired & irritated, I replied "Take that up with your mob on the ferry----they gave it to me in my change!"
Rather than argue with a clearly "aggro" Aussie, he conceded the point.
English businesses even looked "fish eyed" at Bank of Scotland notes, despite
those being legal tender anywhere in the UK.