I'd say the driver was at fault, however the cyclist should have slowed down and tried not to go over the roundabout. Whether in a car or on a bike, always approach roundabouts at such as speed as to safely and easily stop. This also reduces the risk of more serious injuries associated with being hit from behind, due to the reduced speeds. And never assume people will see you or cede priority, especially when you're on a bike. I get this every single day.. being squashed in, forced off the road, verbal abuse etc. This country is shit when it comes to cycle provision.
Just to confirm, you were following at a safe distance and within the speed limit? This is not to say you weren't, by the way. Just a means of trying to establish the circumstance. If these people are intentionally driving round looking for trouble then the public and the police need to be aware. I wonder why someone would do that.. well, one can only speculate. Some do it to try and rob people. Some do it for fun. Both groups are are ass-holes who deserve everything they get..
Total prick...the drivers got mad cos he won't admit he didn't see the cyclist... What a twat