It's difficult to find an exact match in case of the landscape, but if you take a bit wider range, I guess you're right about the location. And a proof for filming of the roof: you can spot a little bit of the roof while filming Hawks Tor China Clay works and even a bit more filming at Tedburn Rd.Looking at this one again I'm pretty sure this is a match. They seem to have been filming through the roof on this stretch of road.
Then for the 'INN' location is it possible to date? Just before the leave the coach it's 14:10h? If it is on the 15th, then it's about 100km after Graddon Cross (12;18h) cruising speed approximately 50km/h and perhaps before Taunton?
In the odds and ends of the footage there seems to be a link with the 'umbrella' scene with Mal (14:30h); it's raining, and they stop at an Inn/ Pub/ Restaurant.
fl.