AOG, on what evidence, on what basis, do you believe the story to be true? The story appears to originate with the Mail and been copied by the Telegraph. It is not in 'a paper of record'. The evidence is from one anonymous shopper, and an anonymous spokesman, whose status is not given,and M & S themselves make no reference or allowance for the practice in any of their rules, policy statements, or guidance for staff.
Do you not think that, if this was policy in even one shop, the Mail would not find one shopper who suffered it and who would give their name ? The refusal could hardly be unique at this time of year or at all. Could they not even get a reporter to the shop to try it ? They could take pictures too; if they can inform us, by a helpful photograph, what the wine shelves of a supermarket look like (goodness, I never knew: I suppose the Mail thinks its readers need to be shown too, otherwise what's the point?) they must have enough imagination to do that, and to identify time and location.