In principle, mess dress should only be worn to non-military events when the equivalent civilian dress is tails. There aren't that many of those, are there? But mark the principle. If it really is a splendid occasion, you might consider mess dress. But what if it's something like the annual tennis club dance? Wayne and Darren may well decide that black tie is a good idea, but might not mess dress be rather OTT? As for medals with black tie, only on very heavily militarily influenced occasions, I think.
But what do I know? I'm an old fart and haven't even worn black tie for about three decades.