I know this isnt for everyone but thought I would share.
On examining my receipt I had some unexplained discounts at the bottom of the receipt - and it seems that there is a double offer being applied to muller light (and possibly to corners).
The original offer was buy 6 for £3 but they had also just reduced them all to 30p each. I bought 12 (banana and custard flavor if anyone is interested) total £3.60. Then at the bottom there are two discounts - -£1.74 and -£0.36, new total = £1.50
Offers normally change Tuesdays I was told by one of the staff so get in quick.