Re: They kinda do and kinda don't
"It can't be 360 degrees otherwise you'd be going back up the road from whence you came."
I wrote "a > 360degree turn". You do a complete circle and a bit more to line up with the first exit. There was no central obstruction in the roundabout to constrain your final line.
Surprisingly there doesn't seem to be an obvious picture of it anywhere. Thinking about it it might have been near Telford - not Devizes. We were on a project and that particular week our regular hotel was fully booked and we had to seek out alternatives in smaller establishments in the surrounding area.