DH saw this thread and said that a real pedant would be less worried about the apostorophes than whether the Pimms was served in the way described on the bottle - with ice, lemon, mint or borage and cucumber skin - or turned into a floating fruit salad. I'm still trying to get him to see the important things in life!
Totaally off topic but my father in law has a recipe for "mock Pimms" which is very good too and a lot cheaper than the real thing. 11 fluid ounces of dry white vermouth, 7 fl.oz. of red vermouth, 5 fl.oz. of brandy OR gin and 3 fl. oz of Cointreau to make a 26 fl.oz bottle of base to which you add lemonade etc in the ordinary way.