Well I'm sorry - the question looked like some scallywag had got hold of a car belonging to someone else - I still can't believe that changing the ignition barrel can have anything at all to do with curing a heater fault but you've changed it anyway.
The thing you mention is usually called a Key-Fob I think - a gizmo to cancel a car's security alarm.
I have no experience with car imobillisers but would suspect that if the ignition (barrel) circuit is disturbed the imobilliser believes the car is being stolen. Nobody here I would guess is likely to tell you how to over-ride the imobilliser for fear of telling real scallywags how to nick cars.
I believe you need a specialist to call on you.
My apologies agian for doubting your true situation.
Good luck...
Peccavi
November 2009