Bought a few things in m and s today. When you get to the till if you have a Sparks Card they scan it and tell you of there are any discounts on what you are buying.
When you are looking at items in thestore though you don't know that. You go by the price on display. Is it unreasonable of the shop not to advertise the discount for Sparks card holders?
I would have thought it would be in their interest to let people know there might be a discount on what your buying.
You won't know till you get to the till.