1999 Mk1 2.5TD 4x4 Total loss of electronics

Hello all,

Just last week, as the title suggests I have lost ALL electrical power in the truck! However, the horn still works.. (No dash lights, mileage counter, lights, radio or hazards)

I suspect that whilst a friend was jumpstarting me from his 19’ plate wildtrack, he has connected to my positive post and then let the other end of the jumplead short out on my engine or body.

Dashboard power was there but not enough for the starter and then suddenly it was not. 
 

In the past few days I have replaced the battery terminal clamps and the first earth strap from the battery to the body. I have checked the 4 fuses I have in the engine bay and they are all good. I have checked all fuses in the cabin and they are also good.

Multi meter readings are showing power on the battery, between the battery and the body, through the fusebox, ignition switch and there IS power into the clocks from the loom. 
 

I suspected that the clocks had burnt out as there was short-circuit odour within the clocks, this has not solved the problem.

From what I understand, this is the last model to not have an ‘ECU’? This was my first assumption of the problem but have been told it cannot be as one is not present? Though there are multiple relays/boxes in both the driver/passenger footwells, could it be one of these?

I have bridged the starter motor and it fires up, proving that it is receiving power.

Would anyone have an idea what it could be? What steps I could take to rule things out/find the cause? Myself and a few other that have looked it over with me are utterly confused at the situation! 
 

Any help or input would be greatly appreciated! 
 

Thanks in advance,

James