Can Anybody Help Please?

Looking for some advice / help because I'm stuck and have exhausted my knowledge. I have a Defender TD5 110 Hardtop 2000. Two days ago I fitted a new stereo, I connected it to the previous owners wiring loom. A fuse blew (the one marked Haz / Int L.P RADIO) under the drivers seat. I replaced it. The stereo did not work. I checked the live with the earth using a voltmeter, the earth wasnt active, there was an adjoining earth wire (the earth for the rear cabin light) I connected the stereo using this earth. (I later realised that this rear cabin light took its live feed from the ignition barrel) The stereo works fine but the engine wont start! I have ignition power etc but it wont engage starter motor. All other fuses and relays work and nothing else appears to not function. I carefully followed TD5 electrical diagram and tried live wiring the the starter motor from the ignition barrel and later from the output of starter motor relay. Engine starts but appears to have no fuel and cuts out. My best bet is that ignition problem and fuel problem are due to ECM fault, either caused by me or not. Does anybody have any advice, suggestions, ideas as to what I have done, what I can do. I Know I shouldnt touch ECM, (and wont)
but I dont want to get charged a fortune by Land Rover diagnostic people. Is it something simple like knackered ignition not sending the right signals? PLEASE HELP ME Steve c

join the aa then call em out, that ay you get free diagnostics, fer just 39 quid a year

Sounds like a problem i have just had with the series 3, sounds like your iginition switch is shagged, try replacing it and see what happens?

Thanks for the reply. I really hope it is the ignition, do you think thats more likely than frying the ECM? Are there any tests I can do without replacing it?
ps Nice idea about joining the AA, dont think they have the right equipment for Land rover Ecm diagnostics and not really relevant cos I am currently stuck in France

Anybody else got any ideas?

you may have fried the 10AS ECU (green one behind the dash cluster)
or cut a power/earth feed to it.

Basically whats happening is.........the engine starts but the engine ECU hasn't recieved the immobilisation code from the 10AS ECU so the engine cuts out after 1/2 second or so, even if the vehicle has no alarm/immobilser, these ECU's are still fitted

thanks for the reply, interesting! I did take dash off to look at back of ignition and did see that green box, didnt know what it was for. Makes sense though, I hope you are right!
I spoke to a friend of mine who is a lot more experienced than me with Landys , although he has no experience with ECM related problems, he said that I should try live wiring the stop / start fuel solenoid attached to the fuel distribution pump on engine, he says that that part is obviously not recieving the information from somewhere telling it to send fuel, whether that is due to the ECM being buggered or another electrical problem ie ignition etc. That would not be solving the problem but it would at least get me home to where I have my tools and access to another vehicle. Although I am not sure that live wiring more things is such a good idea cos I dont want to mess around with or risk messing around the very expensive ECM. If I can actually find and fix the problem it would be much better. I will check out tomorrow what you suggested - Thanks again mate
Any other ideas from anyone appreciated!

Morning
Have opened the green 10as ecu unit, no obvious sign of damage, I thought I would be looking for fuse but I guess by looking at it, that it either works or doesnt! You say it acts as an engine immobiliser, is that all it does? There are lots of wires connected. Are there any tests I can do? Can I bypass it?
Still confused by whole thing and sods law its ****ing down today!
Any ideas? Steve