landrover starting problems

firstly let me say hi to you all as a new member.

I have recently started having starting problems with my 1992 defender 200tdi. it works for 1/2 the day first time on key then decides to give up the ghost giving just battery light and oil pressure light;
fully charged the battery and checked it with two different meters
checked starter via cable from positive battery terminal to starter motor (started)
engine earth jumper lead from negative to engine block (no start)
have checked continuity of red and white ignition lead shows good continuity
only thing i can think it may be is alarm immobiliser unsure of type (aftermarket)
or prc6913 heater plug solenoid any suggestions before i just put a push button on it? appreciate any responses

welcome.

decent nick 200tdi doesn't need plugs at these temps.

i'd look at your immob when it mucks up again.

however, it won't harm undoing and cleaning up the cable lugs.

For what it's worth I had intermittent starting problems on mine (a 2006 TD5) which turned out to be a spade connector on the wire that goes from the ignition switch relay to the solenoid on the starter. I had all sorts of complicated ideas about immobiliser problems, but in the end it was really simple.