Your correct Alan his office was as you have described. Next to his office going up the corridor was the lounge were they often held a late service (epilogue) this was done by the YM leader usually consisted of a Bible reading and a short prayer.
I remember Owen Humble and there was another guy called Bill that did a lot of work behind the counter selling cups of coffee, Pepsi and the likes. The dark room was as you have indicated but it was further up the corridor.
I was a member of the old stone building as well as the new building. It cost two and six pence a year (subs) in the old building but I can't remember what the cost was in the new building. A friend of mine who still lives in Bedlington may still have his original membership card. Next time I speak to him I will ask if he still has it, if he has I will try and get a copy and will post it on here.
Great days, fond memories were did all the time go?