At Tesco St Austell they have the 8 pack of Wrigleys Extra, both Spearmint and Peppermint, at £1.02, works out at 12.75p per pack, even less that the recently posted Morrisons deal.
Not sure if this is store specific.
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Just remember to wrap it and bin it! Unless of course you are a chav In which case throw it on the pavement right outside my blinkin' door!