Xjs won't start

Hi All

New to the forum and hope someone may be able to help.
I have a 93 xjs 4 litre manual which was working great till yesterday.
Came to start it and it cranks over fine but will not fire. I also have lost all power to the dash no lights guages or anything plus no wipers, headlights etc etc. The only electrics still working are the radio, heater and seats.
I have a Laserline immobiliser fitted which does appear to be ok as if on normally it won’t even crank although I know laserline immobilise more than one circuit.
I know it’s an electrical fault just wondering whether it is the immobiliser failing to energise the ignition electrics or whether it is a electrical fault on the car side.