"Well, I've used the card loads of times and no probs - and also at the Rivington Grill, where a group of 4 of us ate with 50% off. Thought I'd keep receipts to see if I saved the cover price of the card - within first 2 months had saved over £200.
Some of the restaurants do get shirty if you don't mention the card when you ask for the bill, but I suppose if they have to go re-calculate then it can be annoying. If you tell them in advance and give them the card then, in my experience, there'll be no problems.
So cheer up Cathie.