Thanks for your very prompt reply.
I have only limited knowledge of electrics, but I suspected that there should have been an earth from the unit.
Now back to the contractor,- he better come up with a good answer!!!!!!!
Appreciate your confirmation. Very grateful.
We had a shower unit installed two months ago.
The double pole ceiling pull switch malfunctioned and I obtained an exact replacement and fitted it. It is working okay.
However on reflection something is worrying me, - there was only one earth wire - which I assume is from the consumer...