changing a CU were the lighting circuits have no cpc, customer (against advice) dosn't want any more disruption since the house has just been re-plastered, so all metal fittings and switches need to be changed to plastic.
Now I would just go and get switches with the caps, but customer is one of them that runs out and buys materials themselves, then rings you thinking they're saving money. So they have heard me say plastic switches and run out and bought (you guessed it) standard plastic fittings, hence the need for a non-conductive screw such as, nylon or plastic.
If I can I dont want to be waiting for an order from the net
Cheers