Anti hijack "possible theft"

I have a Jag (2000 S Type 3.0 V6) ... was in an accident and
had to replace dash and steering wheel after airbags blew
up. Replacement dash came with cluster and the garage
recklessly fitted the dash with its cluster (instead of
retaining the original). End result (even after putting back
original cluster): car alarm goes on, light on top of dash
rapidly flashes, engine won't even make a sound, diagnosis
reads "possible theft" . The steering wheel drops everytime
the key is placed in the ignition though, so there must be a
little recognition. No?! Is there a way of convincing the car
that everything is alright... a more manual way of reseting
it.