Each time I've used mine in the past , the shop workers/bar staff don't seem to have been told anything about their offers with it. It's always been honoured after checking with the management, and a few times phone calls being made checking up on it. But made to feel guilty using it !
One time (few years ago now ) was actually in The Swan with an offer on pizzas. Bar staff didn't know anything about it, resulting in big discussions between various members of staff before it was agreed that it must have been something they hadn't been told of after I showed them a copy of the offer I'd printed off.
Very embarrassing in front of all the other customers, and made us feel like we were asking for something for nothing! I couldn't eat up fast enough to get out of there that evening. That was the last time I used it, it's now sitting in the kitchen drawer .