"I'm not actually aware of a rule like that over here, from the Regs that I have, you were required to Earth everything"
While it had been required to earth all GPO's since the late 50's, lighting circuits lagged behind.
The 1968 wiring rules still don't specify earthing lighting circuits unless there's a metal fitting on the circuit. Needless to say, there's a lot of flourescent lights retrofitted in old houses which aren't earthed.
That was changed in the 70's sometime and even if there's only and only ever will be plastic batten holders (ceiling mount bayonet light socket for those unfamiliar with local terminolgy), an earth wire must be provided at every fitting.
And while where on lighting circuits, 1mm seems to be quite freely available here. (I have to admit having to use it when out of 1.5mm, but I'd prefer not to). Still, it's better that home handymen use that if that's all they can find in the hardware store, and not just run figure eight lamp cord for extra light fittings as I'm sure most of us have seen. I won't get started on the 2 wire extension leads and extra GPO's wired with the same stuff just yet...
