1.6 16v Dynamique Non Started

[OlderMan]

I've posted on other threads but felt it was time for a summary.

I did a swap and got a non-running 2003 Mk2 3 door 1.6 16v Dynamique spec. Megane.
Mechanically I could find nothing wrong with it. I got a Code Reader, which after I bit of trial and error, reported no stored codes. The Fuse box is clean, dry and no corrosion. Petrol ok, Air cleaner, checked, etc.
I got a roving mechanic out and he basically did everything I had done, only with bigger tools, bigger diagnostics. He came to the conclusion that it must be the Engine Management Unit. I have read up on this system, a lot of information available on the web, but not always the clearest.

I stripped out the Steering Lock, the Card Reader, ECU and the UCH. I opened them up, which is easy to do and found two burnt areas on the UCH (this is the one under the dash, not the engine one, Haynes refers to it as a Multiplex Module). Result.
All of these are "coded" to each other and need to be swapped as a set.
I got all of the above from a scrappy for £50, same year, same model. First thing I got was a fault code, Camshaft Senor, new one fitted, code erased and not returning. Good.

But the car still will not start. It throws over easily, no fault or warnings, no stored or pending codes. There doesn't seem to be a spark or fuel running. I have already checked the fuel pump and it runs ok.
The only thing I haven't changed is the Engine "Multiplex Module", not the ECU. This seems to be also known as the Fuse box but I think they may be different. This Multiplex is a flat panel with fuses and a small upstand at right angles at one end. I think the upstand is the Multiplex (possibly also known as a PSU, Power Switching Unit). For what is been written elsewhere this shouldn't be coded to the rest of the system. This unit seems to be sold separately for replacement of wet/corroded fuse boxes. There is a power feed from this unit to the fuel pump. I can't find a diagram for the ignition, so don't know how it is fed.
So, can anyone confirm that the Fuse box/PSU/Multiplex Module is what I think it is?
Is there any way to test on the car?
Is it coded to the other parts?
Anything else which might be stopping the car running?

Any help appreciated.