I don't suppose I've actually watched "Are You Being Served" for many years. The beauty of this kind of comedy is you don't really have to watch it as long as you carry it around in your head. It's like the Carry On series. The predictability is what makes it work. The plot is only there to provide excuses for the characters to behave in stereotypical ways.
Mrs Slocum (what a wonderful name that is) embodied a stock character that you can find in English literature as far back as Chaucer. She was the lady of a certain age who kow-towed to her superiors, lorded it over her underlings and yet remained immensely vulnerable to flattery, particularly of a romantic nature. Mollie Sugden was a master of this kind of characterisation. Her lines came front-loaded with flowery pretension before souring into fish wife abuse at the end. She was high and low in a very English way. You could smell the face powder and the "products" in her hair but she could probably look after herself in a scrap in a dockside pub.
Of course a dockside pub is as much of an anachronism as Grace Brothers itself, which had probably gone out of business by the time the series was first launched. If there are any Mrs Slocums still around they're not wearing corsets or sitting at home with their pussies. Nonetheless the joke embodied in that character, just as the joke attached to the characters played by Charles Hawtrey or Sid James, chuckles on down the years.