How do I bypass the immobilisor in my Fiesta XR2i?

I have a Fiesta XR2i 1990 (H) and whenever i run the car and then turn the ignition off, my immobilisor resets and i cant start the engine again for 5/10 minutes. The car runs fine apart from that! The immobilisor is on the key when it goes in ignition,not with a fob or anything,so im presuming its standard. Is there any way i can cut a wire to get it off or bypass it,rather than spending a fortune on an auto electrician? Any help would be very very appreciated! Thanks