Immobiliser help needed Berkshire

After the recent attempt to try and pinch my cabby, I now have problems with my immobiliser.
It could be connected or coincidence?
The car will not start and the alarm just sounds as it would if it were armed when it is actually dis-armed.
If I connect jump leads to the battery it will turn over but not fire up.
I have a spark and fuel but no attempt at starting.
The original garage that fitted it are no longer trading so I am after someone who can disable or repair it in the Bracknell/Berkshire area… :dontknow: