Ok here goes...
Here are two aerial pictures of the roundabout in question:
The first image shows the roundabout in question. The second image shows my line in green, my best guess at the drivers line in red, and where I would cycle to be in the primary position all of the way round in yellow.
Now just imagine I am Taggart and I am explaining the scene of a crime

:
Look at the first image. What I want you to look for on the west exit is dirt. Where is the dirt on the road? If there is a preferred path that cars take they keep the road clean and dirt accumulates everywhere else. So looking at that exit you will see that cars don't seem to follow the road marking here. They take more of a racing line, cutting across the lanes a little and cutting close to the left pavement on the exit.
Therefore, it is cars doing this that I have to stop cutting me up. Looking at picture two you can see the line I take. I don't take the racing line on the roundabout as that would bring me into conflict with cars turning right and possibly traveling faster than me. So I stay in the outside lane of the roundabout, but in the primary position to ensure I am visible. I have found from experience that if I take this line cars have two choices, either to sit behind me, which the vast majority do, or to try and undercut me by swinging right into the right turn lane and overtaking me on the roundabout. I have no way of stopping this. That is why on the roundabout I glance back to make sure no-one was doing this. They weren't.
As I exit the roundabout I do not keep primary position, because if anyone decided to take that extreme racing line I would come across the front of them bringing me into direct conflict and danger. Thus I slot into the normal car line which is close to the pavement and from there I follow the normal path that cars take, which again can be seen by looking at the dirt on the road. IMO this is the ideal line, whether or not there was a cyclist hugging the curb at this point. However, if I feel the presence of a car behind me just before I exit and I feel that they are going to pass me too close I sometimes chose to take a more secondary line on exit. However, this is my second choice as this takes me out of the flow of traffic and I then need to try and re-enter it with the problems that entails.
The red line is where I am fairly sure the clio driver went. On entrance to the roundabout he must have taken the right hand lane (which is right turn only), when I was on the roundabout and I looked back he would have appeared to be turning right, which a fair amount of cars do. However, he was going straight on and came off the roundabout at the extreme right of the lane. Had I been in the primary position we would have came into direct conflict much sooner and at a more dangerous angle.
As you can see from the pictures as you exit the roundabout the pavement swings away from the road, i.e. the road widens to allow car parking. This makes it appear that I swing out as I exit the roundabout. I don't I take a smooth line following the normal flow of traffic. This chap takes the wrong lane on the entrance to the roundabout and on the roundabout itself and exits very late and comes into conflict with the normal driving line, and me. Also note that the only other person who was there, the clio driver does not claim that I swung out. I am sure he would have mentioned it if he felt I had.
Now some have suggested that I should have stayed in the secondary position and behind the cyclist. However, as I have explained I was taking my normal line on exit of the roundabout which has over the last two years has served me well. Yes if I followed the same path as the cyclist in front I would not have come into conflict with this chap, but that takes me out of the flow of traffic and can often (although not on this occasion) take me directly into parked cars.
Finally note on exit to the roundabout I do glance again behind and I see the car coming, however, as I am passing a manhole cover on my left I decide not to swing left to get out of the way of the clio. This manhole has a damaged surface around it and ideally I avoid going into it. Of course if I felt in enough danger I could take this course, but on this occasion I felt safe enough to continue on my line.
So final summary, I took a legitimate line, he didn't, and because I didn't hug the curb as he wished he hit his horn. That to me is a bully.
I put this post in preview and I was shocked at how long it was, so in the end I couldn't be bothered fully proof reading it! If there is anything I haven't covered or any questions you have feel free to ask. Although I do have work to get on with today!!