02 Escort 55 1.8TD Immobiliser light not on?

I changed the head on my work van. Started fine the next morning. Ran ok going to work except for a bit of a hiss whilst accelerating.(turned out to be the hose had split where it connects to the turbo) Parked up at work and looked under bonnet to find quite a big oil leak. Couldn't see where the oil was coming from, so decided to start it to see if I could spot the leak. Basically, it wouldn't start. Tried everything from jump starting to bleeding the system. Eventually called RAC, who told me that the immobiliser LED (under the clock)was not on, causing the pump the shut off. Checked all fuses under drivers dash and maxi fuses next to battery. All ok. Checked all wiring connected to pump and all seems fine. Disconnected the wiring connector that's connects the injector pump to the loom. When I reconnect it, I can hear the stop solenoid clicking, but still no light on the dash. I've looked around the usual forums but found conflicting answers with regards to whether diesel pumps are tied into the PATS system.
Can anyone help?