Jiboalee, the proportion of rear end collision for cyclists is about 5%. I suspect that this is because drivers can, actually, see a cyclist directly in front of them. While there is a possiblity that a driver, looking to the right on approaching a roundabout, might hit soemone in front of them on the approach road, it is more likely that they will hit a cyclist who is on the roundabout. Please see Cycle Craft for the drawing of the driver's field of vision.
As for the chances of a PCSO being correct about the safest way to teach children to ride safely, I'd say they're pretty remote. And I speak as one who has had the task of teaching them how to do so on bike patrol.
Riding in the centre of a lane where there are parked cars, i.e. primary position is the correct way to do so, whereas riding more over to the left puts the cyclist in danger of being doored.
However, I'm sure the Bikeability people will be happy to take any of your suggestions, concerning the proper way to teach kids, on board