my 1999 marea td 1.9td100 started to show a orange keycode light on the dash today. on trying to start the engine turns over but glowplug light doesnt light. garage says blue key not being recognised. ( i dont have a red key .. doh !!)but an hour later the fault went off.. phew !! mechanic i spoke to seemed to thinkthat it might be possible to remove the disabling from the fuel pump as it seems its only a solenoid in the fuel line. has anyone tried this or does anyone have any other work arounds for this problem ??

you are correct the immob simply disconnects the fuel pump's earth, if you give the pump a permanent earth you will bypass the immob.

however you dont need to do that, the fact that your fault is intermittent shows that you have the common connector fault. this is usually the connector on the aerial around the ignition switch or the connector in the codebox near the fusebox (in front of driver's right knee). wiggle the wire and its fixed, or even better take the connector off and stick it back on, do that a few times and the fault wont come back for a few years.