Citroen Xsara headlight beam not switching on/off

The dipped beam setting does not come on immediately with the stalk switch. After about 4 mins they come on (switch still on). Both sidelights and high beam ok. Turn switch off and lights stay on even with key removed. I have the mk2 Picasso with the fuse-box with no relays. I was told probably the comm2000 unit so i got a second hand one with correct numbers from E-bay but still the same. Both old 2000 unit and the new one show the light indicators on the dash (green=dipped/blue high), so i'm beginning to think this is not the unit at fault. I have a diagnostic tool but does not show any faults. I have also had the B.S.I unit out and given all contacts a good clean. Has anyone had a similar problem and found the solution? All i can think to do now is to start at the headlamp unit and clean up all wire ends and contacts working my way back.