It's not something I've ever done. It would look better done by you (to make clear it's not a hostile action!). If I were doing it, I'd start with the Wiki: osm.wiki/Change_rollback - is that any help?

I've noticed poor alignment of aerial photography in other places - most notably on steep slopes such as this zig-zag ascent west of Torridon: osm.org/#map=18/57.55422/-5.54483

Yes, my visits there (including a transit of the natural arch) corresponds much better with the OpenData outlines than with Bing aerial. I can probably dig out my track logs if you need to see them.

This outline appears very badly aligned, compared to OS OpenData and confirmed by my personal traces. Please can you revert this change? Thanks.

I was using StreetView on http://os.openstreetmap.org/sv/ - it seems not to have been updated since November.

I've changed the ref to A4017 as you suggest, and set old_ref to avoid any future confusion. (changeset 26762646)