Intermittant non starter

my 406 2lhdi has recently started flashing up various faults on the dash display,ie abs fault anti pollution fault low brake fault engine management fault.then clears itself car runs great.couple of days back car would not turn off on the key .ie ignition turned off key in my hand engine still running ,when i put my foot on brake pedal engine stopped.but the displays on centre part of dash lit up and refused to go off, disconnected battery for a while reconnected and every thing returned to normal,then this all happened again ,but now its flashing up immobiliser fault and the car wont start,disconnect battery again and sometime it starts other times it flashes up immobiliser fault,now it wont start again so cant get it to a garage to see if they can check it out,any suggestions or help would be very appreciated