plan123
Forgive me, but you seem to be making more of this than needs be- its not the Masons! If you meet the requirement for membership (you'll find that on their website) then simply find out when the next meeting is (give one of the member airlines Ops Managers a call and get the Chariman's number and call him) I'm sure you get an invite and warm welcome when you go along; after a few meetings you can then judge for yourself if its of value to you.
UKOMA is a useful forum for ops managers to discuss their and industry issues, for example; ATC, new legislation, ops officer recruitment and training, IT systems, commnications etc. Occasionaly, they'll be guest speakers from agencies or company's wishing to sell their equipment or systems. Visits to the likes of Swanick are also know to happen. UKOMA has always been particularly focused on Ops Officer training and has run courses going back over twenty years- many reading this will have been on them.
I go back to the late 80's with UKOMA and my involvement was always fruitful and I have made friendships there than continue to this day- don't worry it isn't a 'closed shop'.