Frugal postage

When I needed to post a letter or card the old me used to grab a book of stamps at the supermarket.  This used to cost me an arm and a leg, particularly as 2nd class stamps are now 50p each.  What I do now is walk to the local Post Office and buy 1 stamp.  This is doubly beneficial as I get a bit of exercise walking through a park to get there and I only spend a few pennies.