The whole point of a TT supply is that there is no earth terminal provided by the electricity supplier so it matters not one whit if the street cables are SNE or CNE.. If there is any connection to a  DNO earth terminal, it is not TT.

The neutral will have company electrodes in the street of course but they are one component of your 200 ohm or so reading, though hopefully no more than about 20 ohms or so of it and probably quite a bit less. Hopefully most of the 200 ohms is the local house electrodes.

However, if there if there is a low impedance between N and CPC on any circuit, rather than N and terra-firam earth,, then there is most likely a real problem, such as a short from neutral to metallic plumbing, or perhaps could the lighting circuit supply an outside light screwed to something metallic that is solidly earthed outside - fence posts, bollards that sort of thing ?

Mike

The whole point of a TT supply is that there is no earth terminal provided by the electricity supplier so it matters not one whit if the street cables are SNE or CNE.. If there is any connection to a  DNO earth terminal, it is not TT.

The neutral will have company electrodes in the street of course but they are one component of your 200 ohm or so reading, though hopefully no more than about 20 ohms or so of it and probably quite a bit less. Hopefully most of the 200 ohms is the local house electrodes.

However, if there if there is a low impedance between N and CPC on any circuit, rather than N and terra-firam earth,, then there is most likely a real problem, such as a short from neutral to metallic plumbing, or perhaps could the lighting circuit supply an outside light screwed to something metallic that is solidly earthed outside - fence posts, bollards that sort of thing ?

Mike