So I delved a bit deeper and found https://www.sustrans.org.uk/pathsforeve ... tion-plans
and they're doing basically naff all in the East of England except for small reroutes in Cambridge and Dunstable. Nothing to close the three gaping holes in the NCN (roughly Breckland and Forest Heath, around Diss/Eye and around Haverhill). Nothing to remove the bizarre detours. Nothing to remove the no-cycling-allowed sections. All little fiddling around the edges which won't make the network safe for children any time soon.
I think (happily) the situation is better than that. The plans only have what Sustrans are calling "activation projects", but I've also heard them called "demonstration projects" and elsewhere they might be called "pathfinders". Basically the idea is to start with a small number of geographically dispersed, isolated examples of what could
be done. Experience from these will then be used to go out and say to funders "look, this is the sort of thing we want, now let's roll it out over the entire network". So, for example, the Lincoln activation project would be a demonstration of how to fix no-cycling-allowed sections elsewhere (the blurb says "Replace damaged signage and remove traffic regulations that restrict cycle access").
Meanwhile, Sustrans is putting together network development plans, roughly one for each county. These are the detailed lists of exactly what Sustrans wants to do in each area to make the NCN top quality. I've been peripherally involved in the drafts for a few of these in the South region and it absolutely is about making consistently good routes in both urban and rural areas, rerouting onto segregated cycleways, developing rural quietways, removing indirect routing (and, sometimes, entire routes that can't be fixed), all of that. It won't happen overnight but the aim is very much to fix the whole network, not just a few issues here and there.