Central locking not working on 2003 Relay 2.2 HDi?

[Taipan]

Hi All

Recently picked up a 2003 2.2 HDi Citroen Relay. The central locking doesn't work at all. Its completely dead and doesn't work by either remote fob or by turning thekey in any lock, or by using the door pop up button things. I dont have a manual or wiring diagram and apart from checking the fuses, which are all fine, I'm not sure where to start? Is c/locking
controlled by a relay? Any ideas on where to start looking/testing?

I did the BSI reset thing but it made no difference.

Many thanks