I hope my comment is not unduly harsh. Tragic outcome and every sympathy to the victim's family. And I'm sure it must have shaken up the OP and others who use that junction.
But: there's really only one rule that needs to be observed at mini roundabouts, and that is, traffic approaching on your right has priority. Even if it's not yet anywhere near the roundabout. Keep that in mind and you may survive. Insist on only giving way to vehicles already on the roundabout (as the HC suggests) and you may not.
I need to negotiate lots of mini RABs and, as often as not, there's a long line of cars approaching by the exit on my right. I let them all go. Not to do so would be suicide. Sometimes another vehicle already on the RAB will block the line, giving me the chance to slip out, but not always.
So the question is, if the cyclist was travelling south towards the RAB, and the car was travelling east towards it, the car had priority. And I'm afraid the cyclist would have been at fault. It looks that way, comparing the press photos with the google street view: the bike seems to be lying on a grass verge to the east of the RAB, i.e. the nearside facing south. But if I'm wrong, please correct me!