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How much self-support do you need? It's best not to stop too often as it obviously takes time and the temptation to not get back on is not helpful!
I've done two 12 hours unsupported and planned on a one-stop stategy for each, so only needed to get to my car at about the 7-hour point.
Admittedly on one of them I dropped a bottle so needed a second stop at about 10 hours for a final bottle.
I've found one Strava activity for the D12/1 and it looks like there's a middle section which doesn't go near the Prees Heath RAB. Looks a bit undoable on an unsupported basis if that's still the course.
The northern circuit is worse than Newbury, by a considerable margin. Lane-wide bone-jarring trenches all the way across the road. Plus potholes. The smoothest line is to try and ride along the rumble strip by the side of the carriageway. It's smoother than the road surface.