It's on an internal door and its an Era 3 lever mortice. It's an old property & I thought I'd bought a new one (which was exactly the same) to replace the old one because we've never had a key to it. The new one doesn't quite fit.
I guess it's probably more a joiner or handyman we need.
That is exactly what I did when first bought the new one.
Unfortunately the existing one is old and apparently not a size that is readily available anymore. The new one is just ever so slightly too large and since I'm no expert I prefer to get someone in who knows what they're doing.
So I came on here hoping someone would be able to offer the service or recommend rather than just pick someone by chance