Sure you don't fancy a drive over GK?
Here are the latest exciting updates
*With the switch not connected the fuse doesn't blow. (i.e. the light is hard wired to the lightin circuit).
*With the switch connected the fuse blows.
Guess this wouod point to the switch wire, however a check with the meter shows no problem. No leakage between phases and everything connected as it should be.
Further checking the phases at the rose on the main there is a low resistance between earth and neutral. Since I'm not clear if this is to be expected I think I need to get a man in...