Ah, sorry.
Mutual Society. ie, still truly owned by its members, rather than shareholders. Lots of hoo-hah about this in last 10 years as many UK Building Societies "de-mutualised" with nice windfalls for existing members (ie, savers or mortgage customers) but then exposes the former societies to standard vagaries of the stock market, acquisition by larger groups, etc.
Standard Life is the latest, and one of the largest, to finally give in to the draw of big initial windfall benefits for directors and members...but the long run (IMHO) means poorer service for the customer.
All down to the individual, of course. But I have been very, very impressed with YBS products, customer service and flexibility. Can tell you more if you are really bothered
Campbell