Something to think about, Ric, would be having the system inspected. It's called a "periodic test", and it's usually carried out every 10 years.
The electrician would test all circuits, including the problem one. By the time you've paid for call-out and the rest, it would be better value for money to have the peace of mind of a full inspection. Test results would decide if a complete re-wire is necessary.
I'm loathe to give an idea of cost since labour rates vary considerably. If I say around £200, then I'll probably be shot down by someone.