And the freezing fogs of those days, with the A1 not fully dual carriageway. Car nav. was aided by the mileometer ["turn right after 4.3 miles ...."]. Wind the windows down to listen for traffic before turning right.
But we had many many observations from many many RAF bases, staffed by professional observers. These were supplemented by AA and local council basic-trained observers which meant that [although the forecasts were a bit iffy] the actuals were plentiful so updates were always available to the decision takers. Even the aircrew sometimes passed us a cloudbase on take off, helping to calibrate our Mk I eyeballs.