I think that you're going to do a lot of work for very little or no result. This forum's membership simply isn't big enough to persuade most retailers to go to the trouble of putting in a system so that W.C. members can get a discount.
Let's assume that I'm a retailer in northern England (which I am as it happens) and you approach me with a request to offer a discount to your members. My first question will be "How many members do you have who will have this card?". Presumably you'll be honest and say "About four or five hundred" and that's assuming a big increase in those who have voted.
So I say "So I can assume from that, that in the NW of England I may have about 100 of your members?"
Well, I'm sorry, but I'd need a lot more than that to persuade me to go to all the trouble of putting in the necessary system so that my staff can deal with it quickly.
Also, how will you handle purchases made online or on the telephone? How is the retailer going to know that the person buying his widget is actually a member and has a bona fide card?
And next thing, I get a phone call from the northern branch of the Tent Camping Association and then the Lancashire Trout Fishers Club all asking me to give their members a discount. Where will it all end?
It's thoughtful of you to try to get a benefit for your members but I really do believe that you may well have to do a large amount of work for no real result. Save your energies for this site!