Crack on? 
If as described the roads are twisty, with solid white lines, I can only reiterate that someone shouldn't be overtaking, unless they want to feature on cyclist's camera compilation on YouTube entitled 'douchebag drivers part 126
I don't think I've ever seen a cyclist doing less than 10 mph in such conditions. I generally go faster than a lot of cars when I'm cycling round urban areas.
Clearly alot of drivers have hate to others on the road from their more important than you attitude. If car drivers don't like the roads and conditions on them, get off them.
There, cracked! 
This is a sticky point in the highway code and it illustrates how out of date it is. I says that you can cross the double white line for a slow moving vehicle such as a cyclist if they are travelling slower than 10mph. Now, even on the hills I barely get below that speed but do I want a motorist stuck behind me for several miles while they stick to the letter of the code? Nope, defo no way. It is about sharing the space. Some can, some cannot. Some misinterpret a helpful gesture as a somewhat spiteful move.
There is a rather difficult road near me where you have a steep climb with a very blind summit and a chicane to boot. It's an old B road but well looked after so the motorists give it some welly. As you approach the chicane you are doing barely 8mph and you have a possible scenario of a fast moving motor vehicle misjudging the situation and thinking that they can go for it. Now as a cyclist you are in front and sitting higher so you can just about see over the summit to see if it is clear, the driver cannot but you know that some of them would risk it and put you in danger. If it is not clear you have a really bad scenario unfolding. Now this is where it gets interesting because it can require a big set of balls to take the Primary position (centre of the lane) to block said vehicle (with enough notice and not so as to cause heavy braking) with such a speed differential and a vehicle closing in on you behind you (that you cannot see). So I also put my hand out to indicate stop, I make the deliberate gesture of craning my neck over the horizon and keep my hand up to say Stop. Now at this point drivers sometimes gets very irate until they see said vehicle thunder past in the opposite direction and you move over to let the driver behind you through and gesture thanks to them.
This is what I mean when I talk about people misunderstanding other people's actions on the road. It is easy to understand why a motorist does something, because you are one yourself and you have likely been in a similar situation once. If you have never cycled* you cannot fully comprehend the actions a cyclist will take to make their ride safer, such as slowing down through a twisty section or riding in the middle of the road where the traffic island creates a space that is too narrow for a car to pass safely.
So, can we leave our opinions of that one/two/three bellends we came across one day and who we still channel our anger towards and talk about this rationally? I think that there is value in proper discussions on the topic rather than bleating on about 'this guy did me wrong!' (sob sob, woe is me sh!te) ?
Please?
*riding a bmx when you 6 doesn't count, I mean doing hundreds if not thousands of km a year on a bike. 