I don't think we're being any thicker than normal Phil !
The immobilliser can be disabled using software, but the software needs the code to be entered from the card wot you don't have. And yes, the ecu will stop looking for the key and clocks.
Re-enable it using the same software.
Have you found another way to immobilise it??
Added:
twpd is obviously spot on... don't be trying to mess with circuitry while it's live!
[Edited on 9-1-2006 by NBs996]