You're suggesting the government web page is incorrect?
Yes, I have explained why.
That webpage is not law.
So I leave my house and drive down the road. I don't pass a sign. Does that mean the speed limit isn't 30?
Unless you have your motor vehicles delivered by helicopter, then you would have passed a sign on the way to your house.
I think you're getting confused because NSL is usually used as an abbreviation for "NSL outside built up areas".
I assure you I am not the one who is confused.
So are 60 limits.
There are very few 60 or 70 limit roads, in England at least. You're getting confused between a 60 limit and the NSL, which is variable, but without the aforementioned signage, in a car, on a road that is single carriageway, the NSL would be 60, not 30.
Likewise in molgrip's scenario, if it wasn't for the large 30mph roundels, the regular and obvious street lighting, and the *massive 30mph signs painted on the road, the NSL would be 70, not 30 (in a car, assuming it is actually a dual carriageway).
*actually has no legal bearing, but included for effect.