I'm trying to remember the last time i paid to send something in the post. Not sure i've ever bought a stamp :/
I think you can't buy
a stamp any more. Whenever I see them for sale, it's for a mininum of 6.
I only send 6 things by post per year.
I'm almost sure that the cost of stamps has gone down in comparison with average income.
Now I've made myself curious. The OP used old money, so I'll compare with 1970, the last year of old money.
1 minute of looking and I couldn't find it, so I'll go with the cost in 1968, which was 5d for first class.
In 1968, the average pay in the UK was about £1500 a year. 7200 stamps, assuming that the £1500 figure was in old money with 240 pence to the pound. Should be that many anyway, as the cost of a stamp would scale the same way.
In 2014, the average pay in the UK is about £26500 a year. 42741 stamps.
So yes, the real cost of a stamp has dropped a lot since the days the OP was talking about.