I always wondered about this too, and whether it was right to just go onto the roundabout or not. Have never been quite sure...
A classic case of cyclepath confusion if ever I saw one. Cyclepaths do have a tendency to have their own unwritten, unknown rules and nothing to do with the Highway Code.
Off topic a bit, but...
Here in jolly ol' Milton Keynes, our most wonderfull Redway system (and this section also includes Sustrans National Cycle Netwok Route 51) takes us cyclists to the town centre. But, you go under a road, via an underpass, then come to a road, which you will then follow. You now have a choice. You can turn onto this road and then follow it instead of crossing this road onto the cyclepath. Or is it a cyclepath?
The road is effectively a service road which follows the main road. From this service road are parking spaces for the buildings along this road, so you are really riding through a car park, which is pretty hazardous.
Or you can use the cyclepath. Or is it a cyclepath? I still don't know. Why? Well, there is a sign which reads, "No cycling on footpath."
This sign is the blue rectangle with white writing (Meaning it is a reccommendation, only the red bordered, white circle with a picture of a bike means no cycling) So is it a cyclepath, or is it a footpath?
The Redway guide doesn't show it as Redway, but the current edition is years out of date and Milton Keynes is expanding very quickly.
I sometimes use the footpath/cyclepath.
Should I fess up to the fuzz for illegal cycling? Or am I a goody goody and can carry on as I have been doing?