ibizaboy, i feel your pain!
I work for the co-op and the other week i failed the mystery shopper as I refuse to say the following....
"Have you brought your own bags or would you like to buy one of our 10p reusable bags?"
And the reason I refuse? We have hundreds of free ones on plain sight, and im sick of customers looking at me like im thick when they go "errr no ta, i'll have one of your free ones instead"