I have a grey grim looking lock on the front door of my flat. The closest in design I could see on the internet was the photo at the top of this page:
(except mine does not have those three visible screws).
After an attempted forced entry, the switch on the left seems to be unpredictable, so could end up locking me out. The small ?handle/knob on the right is loose. I know nothing of DIY. Does it sound like an easy mend or something that needs replacing?