Because slip roads branch from a dual carriageway, a roundabout breaks it.

On slip roads that may be true, but for roundabouts no. Funnily enough I tried asking National Highways the other day about speed limits on slip roads (60 or 70) and they basically said "it's national speed limit" (i.e. no answer. I would presume the same for this case, so we can only go on common sense here, in that it's a single circular carriageway, not part of the dual carriageway.

I refer you to the second word of that definition.

One of my recent big edits was removing a dual carriageway that didn't exist, that's not a "lower standard", that's making the geometry fit the road layout.

If you're referring to the road splitting at traffic islands at junctions, it is unnecessary complex geometry when the island can be represented by a tagged node. For more complex layouts or very large islands it makes sense to split the road, however in locations like this it's not worth it in my view.

It is a dead-end road, why should it be tertiary?

Roundabouts are single circulatory carriageways, not a dual carriageway.

Please update maxspeed:type tags when updating maxspeed tags

"GB:sign" is not a valid maxspeed:type tag

What source did you use for the names here? Wikipedia lists the village as "Cross Hands"

Do you think it would be better to tag "lit=no" in such cases?

Please change maxspeed:type tags when changing maxspeed tags

Well, without the lit tag it cannot be determined if the maxspeed:type=sign designation is correct, so it makes sense to remove this tag pending the addition of a lit tag before a maxspeed:type tag. From my experience it's more likely a lit tag is correct than a maxspeed:type tag on a 30mph road.

And yes, technically the road can be lit, with the streetlights further than 183m apart, and not be under a 30mph speed limit, however it is impossible to tell without measuring the gaps between street lights. Large distances are unlikely to also warrant a lit=yes tag anyway. There is a village near me that has a few street lights on a 30mph road, and yet there are repeater signs so it does not qualify as a restricted road, so that's one way of telling.

If there are no street lights then yes please do include the tag lit=no. From my experience it can't be assumed that the road is lit or not depending on the maxspeed:type=sign or maxspeed:type=GB:nsl_restricted tags, as there are so many erroneous applications of these tags out there.

This is not a dual carriageway, so "maxspeed:type=GB:nsl_dual" is incorrect

Hi, please remember to add relevant maxspeed:type tags when adding speed limits. See the wiki page for more info: maxspeed:type=*#United_Kingdom

No one else is being linked here and you're just making leaps to open gates on private land now, and *still* talking about signs as if they have any legal meaning! Create a discussion if you want to standardise the tagging on unadopted roads. I will continue to remove access tags as they are routes the public can use.

You don't understand that just because there's a sign, doesn't mean the sign is right...
Please just open up a discussion topic at this point if you want to try and argue your point.

Looks as though the restriction is changing soon regardless https://assets.dft.gov.uk/trafficauths/case-5242.pdf

An unadopted road is not private, it is just privately owned.