Thanks Bob, yes it plugged straight into the grey connector. I was just checking to see if it needed a relay or something.
The only other thing was that the previous owner had a 12N socket put in the boot for some reason. I wrote a thread on that last year
https://www.volvoforums.org.uk/showthread.php?t=328446
Maybe they could have messed up the wiring.
I'll have to do some more checking.
Thanks anyway.