I live in a ruralish area. Most of our local country lanes are NSL - completely inappropriately. Because we have a number of big towns around us, people are always looking for ways to escape the traffic jams and therefore tend to use the country lanes to try and cut through.
The NSL is 60, I would estimate it is physically possible to drive at 40-50 with the occasional higher stretch. These are unlined roads, mostly two cars can pass, but some tighter stretches and some passing places. But while those are the NSL and the possible speeds, I'd say it isn't actually safe to do above 30-40 at most, due to the high number of horse riders, carriage drivers, cyclists & walkers who are likely to be walking in the road around the next bend. So that is the speed I do - what I consider safe for the road conditions. But I almost always, on certain stretches, end up with a load of people sat behind me, as they usually race inappropriately fast through these lanes. Is it my job to police them? No, absolutely not. But neither am I going to be bullied into going faster than is safe or appropriate. And no, I'm not going to pull in either - there are no parking pull ins so it isn't safe really, and these are roads where I live, work and pass leisure time - why would I want to make it easier for people to drive dangerously and fast, when I don't want them driving on lanes I may be walking/riding, going excessively fast. These are not local people, these are people commuting mostly, using M, A & B road speeds on roads that are proper country lanes.
And yes, I do know the size of my vehicle, and yes, I can reverse it, and yes, I have passed an advanced driving test, so no, I am not lacking confidence on these lanes.