Brilliant! Thank you very much.
I looked under the bonnet and the switch has no wires coming from it, so they have obviously forgotten to reconnect it. I have tried looking for any loose wires attached to a connector but without success. Where should I look?
I just found that the wire come in from the rear of the switch, and in fact the switch had been bent down a little as you suggested. Now I have bent it back, everything is fine. Once again, thanks.