2009 Defender 110 TD 5 Ignition switch

Hi guys hoping someone out there can help me really weird things going on with my td5. Firstly when I turn off the ignition switch and remove the key the engine still runs only way to stop it is to press brake pedal. This has been happening for some time now and just put up with it until few days ago when I parked on a severe camber overnight with very low fuel. Landy started in morning ran for 5 min then stopped so put more fuel in and started moved off camber onto flat then cut out so did the old trick ignition on waited for 20 seconds until pump stopped and repeated for 5 times then on 6th time started ran ok took it few hundred yards and stopped again. Now here is where things got strange apart from the engine not turning off with key out. I touched the brake pedal stopped engine so now no power to anything but the fuel pump kept going for about 15 seconds but did finally stop. Here we go, switched ignition back on and the temp gauge was flicking up to half normal temp but engine cold and then was flicking fully to the right and back. At this time I could here the pump and see the heater plug orange lamp, red oil light and red battery light on dash which is normal when starting then switched off removed key stopped engine, then tried again but now no pump running and no heater plug orange light on dash. That is where I have left it, I know all the above is a bit long winded but I thought better to put every detail down. One more issue I found was that my diagnostic unit can't communicate with the ECU but found this problem out early last year when tried detecting another fault so not sure this could be a problem or not. Looking forward to some helpful feedback, thanks.