Light switch earth

[pickles]

I'm just about to change a plastic light switch for a metal one. It says on the instructions that the switch needs to be earthed and there is a screw connector on the back for this. The metal box in the wall is earthed but due to the number of wires in the box it will be difficult to get another earth wire in there from the terminal on the face plate to the connector in the box. Given that the new light switch will be attached by metal screws to the earthed box will this be OK or do I need to run the separate earth to make it safe and comply with the wiring regulations.

Also I am replacing 3 hall light switches on an installation that was done in the late 80's with what I think are Double D fittings, these are different from the ones I have seen before in that they have 4 terminals rather than the usual 3, Is something unusual about this or is still possible to get similar switches. I have heard that double D went bust years ago.

Thanks in advance.

 

[GaryMo]

Earth the metal switch plate.
The switches you're referring to which have 4 terminals are intermediate switches. Any number of these can be fitted in between 2 x 2 way switches.