At the moment in the UK Royal Mail workers are having a series of strikes to get a higher wage. Whilst I can understand workers trying to get salaries that keep up with inflation, there is a great danger of long-term damage to their jobs.
Fewer letters and postcards are being sent these days as people use email instead. They are trying to focus on parcels, but people are finding out there are alternative people who do this at competitive rates that are often cheaper. There is danger people will always use them in future further damaging the Royal Mail's business model, and profits.
See https://www.royalmail.com/sending/barcoded-stamps .
UPDATE 1600z: I have been told by Steve G1KQH that the deadline to use up old stamps has been extended to next July following complaints by customers.