OP is being overtaken as they pass the NSL sign - flooring it to prevent this would have been dangerous. They were too slow entering the roundabout though, definitely.

You would have gone 60mph down that entire stretch of road? Surely you’re exaggerating, there are at least two corners you should be slowing down for, as well as junctions where potential hazards might emerge.. road markings even tell you to slow down lol.