Discovery 2 electrical problems, stuck in west Africa help!

[TheAfricaSchoolRun]

Hi ok I really need some help here mechanics out here aren't so hot....

So I have a 2004 d2 v8, its been in storage in Africa for a year, asked for it to be run regularly but assume it hasn't.

Had to do few bits n bobs to get it good to go on our return journey to UK. Fuel pump, brakes, service.

After few days tootling around with no issues, we set off (4000 mile trip) after 50 miles engine cut out. No warnings of this, although ACE light had come on but had gone off again, its about 40 c in the sun so the heat plays tricks on the car! Maybe something up with ACE but it won't stop us driving home so it can wait.

Engine wouldn't re start. Plugged hawk eye in and it gave an error code about the fuel mixture but we think this may be a red herring as cleared the code and it hasn't come back and there are no other error codes on the engine management system at all!
Re set emergency fuel cut off switch just in case and engine started for few mins then cut out again. This repeated for about 6 hours, at night (when cooler) engine ran for 30 mins then cut out wouldn't re start. Checked all sensor plugs, took them apart and cleaned them, idle air control valve was getting v hot, dunno if it does normally or not, was buzzing slightly too...?

Mechanic took it to someone who has a diagnostic system, albeit probably an old one, he thinks the crankshaft sensor is to blame but is worried for the ecu....! He took crankshaft sensor out, it was full of oil n fillings, cleaned it n returned it and car ran for over an hour, went for second test drive whilst hot and it cut out again, wouldn't start for over an hour.
If its the ecu we are struggling as apparently its hard to 1) get one out here 2) if you can get one then no one can fit it... Even if we tow car to main dealer in Dakar (one full days towing!) they may not be able to do it. We are a bit screwed if we can't get it going!
Someone suggested checking engine earths...?

So questions.
1)Any ideas what else could be to blame?

2) Can an ecu be swapped for a second hand one, what do we need off donor vehicles if so and how hard is it to reprogramme. Or are we better off waiting (maybe a week!) for a new ecu and trying that as maybe its easier to reprogramme??

3) any other idea what on earth is going on with it, seems to be electronic and sadly we are in a bad place to fix electronics!

Ps the ac cooling fan has just been found to be buggered too.

Thanks in advance
James