Old houses move. The opening is rarely the size on the original drawing. We measure what is there, not what should have been there. A replacement that is even a bit off will not shut. Repairs to sashes and sills are sometimes enough. Sometimes the whole unit has to come out. We say which one after we see it.
New openings in a new frame are cleaner. They still need flashing and a path for long frames down a terrace hall. After a demolition, new windows wait on the frame. We can do that sequence.
The wall around the window may be timber cladding or a new frame. We quote the opening and the unit, not a guess from the street.
We inspect, then we quote. Photos of the unit and the hall help. Call 0487 549 909 or send the suburb and a couple of photos.