Funnily, the army doesn't tend to be quite so difficult about that. Most families and people with a connection to the regiment get a number of concessions through either the families office or the Regimental Association. Certainly limited mess privilidges are granted and where the RA is active a number of "old boys" attend guest nights in the mess. I can't understand the mentality behind that, but I suspect it is because you join a regiment in the army, and you join the RAF, and it is much easier to get lost in the system.