Go to Poundland to save money on batteries.All types. Their Hyundai Button batteries, 50 on a card for (you guessed it) £1.00. I have a calculator that uses 2x 389's which the local jeweller charges a £1.00 each (markup of £1.96!).
"All you are doing is removing the 'stronger than usual' wrapping" - True, in this instance yes that is so, but what it fails to advise is that not all cells are constructed of internal separate batteries. Break into the case of a D Cell in this way and you have some pretty nasty compounds on your hands.
If you have a quartz watch, you will normally pay about £4.99 to have the battery replaced at the shop. If you have a Timpsons Shoe repair/watch repair outlet nearby (ours is in Tescos)and pay about £8.99 they will give you free replacements for the life of the watch. This is obviously only worthwhile if you have a decent watch, as its hardly worth it with a £1.50 petrol station one.