I know an even cheaper choc than that made by Cadbury and given away free in most Tesco!
Tesco are selling 2 large bars of Cadbury for £2.20 BUT if you buy 2 large cadbury bubbly the discount doesn't come off, meaning you are charged £1.35 for each bar = £2.70
You pay for the bars take them to customer service and tell them you have been over charged (should of been £2.20 not £2.70) and they have to give you a refund and let you keep the choc
This was still working yesterday and going by Tesco's track record they probably haven't reprogrammed thier tills yet