Hi Dave/Gerry
I had same problem whilst driving to Spain and tried reset code using key in door but no joy, i overcame the problem permanently by connecting a wire to the fuse panel labled A under steering wheel,its the fat yellow wire from the ignition,then i connected this through the bulkhead to the solenoid switch on the fuel pump,this bypassed the immobiliser and have had no problem since let me know if you sorted it or need pics,good luck
Richard