Just been messing about with Google Earth to find the scary road/lane I mentioned above.
I managed to find the (impressive) ruined abbey I mentioned. It turned out to be Byland Abbey. Following the road from there led me to a village called "Wass". There the main road does a sharp right turn and I carried straight on. There are signs prohibiting lorries and traffic in wintry conditions but no gradient or narrow road signs.
I must have missed the lot!!