I mentioned that very junction earlier, before you had finally given the coordinates (do keep up, TB):
http://www.cyclechat...ost__p__1869322
I'll let others decide if they would be comfortable descending down to Totnes with cars potentially passing them in the same lane, with those bends and with that width of lane. I'd certainly be a good 3-4 feet from the hedge. Only a bit futher down, it's unbroken double white lines, so no overtaking there anyway. It's easy to see why a cyclist might have had a queue of cars behind, regardless of whether he was on the phone.
Oh, and I think you mean the A3121, not B3121 through Ermington! This rather proves my point about your navigation and direction skills, don't you think? As it happens, I did use the A3121 as well, but I preferred going through Ivybridge as I would often stop to see my gran.
Letter boxing was good fun as a child (it teaches you how to read a map for one!), but I can't say I've done it for 20 years.
I don't know if your M-in-L is an emmet, but the more you post, the more I feel for her regardless of her Devonian heritage or not!