We used the Tomtom One a great deal while holidaying down in South Ayrshire. It worked very well and guided us to a number of places, including the remote cottage that we stayed in.
We put the postcode supplied to us by the owner of the cottage into the Tomtom and it took us within a 100 yards of the place. I think the postcode designated the area rather than the individual buildings. Without it, I doubt we would have been there as quickly.
Another situation was when I tried to find the Sulwath Brewery in Castle Douglas. We found ourselves on King Street and as Liz pulled over to park, we were right beside the brewery. It would not have been easy to find since the brewery is actually not on the street.