I'm amazed that, in the staff room, teachers don't call each other by their first names. If a colleague in an office called me 'Ms gb' I'd think they were using formality as a joke, or referring to someone else's amusing use of formality.
I suppose the 'Miss and Sir' thing for pupils dates back to when women gave up work after mariage, so all female teachers really were Miss. We called secondary teachers 'Mrs name' but would say 'please Miss / Sir, can I...'
Jokes are funny once and it sounds as though your colleague was trying to be amusing once, by playing the pupil, or with a traditional style but has got stuck. Surely if he addresses you this way in person, you'd ignore him - it's the equivalent of 'hey you' - which 'you' in the room is he addressing?
I'd go with 'my name is lottie, lottie gb and as I'm married, that's Mrs gb. You are welcome to call me lottie but otherwise it's Mrs gb, Mr X. I've told you this before, I can keep reminding you but it really would be helpful if you could try to remember for yourself as it's getting a little tedious, don't you think?'