Thanks Terry.Turn off the power to the circuit at the MCB. Remove the single cable from the switch ( the one that is in a terminal on its own )and put it into an insulated terminal block . Turn on the power at the MCB. If the lights now go off ,but will operate as usual by the PIR's ,then the switch is duff. If they come on and stay on then it's a PIR issue.
I did this and the lights stayed on. So it seems its the PIR. Gonna look for a replacement or a new light.
Again ty everyone.