There is no expiry mraked anywhere on them.

Moreover, given that I have bought 144 of them, there is an implied condition
in my purchase contract that they will be valid for more than the few days
before the price increase, that they will be valid for a reasonable period
hereafter.

If the worst came to the worst, I would have a legal claim against T.F.L., the
newsagent (as their agents) and my credit card company (as the paying party,
who guarantee the purchase).

Marc.