Aye 'Ivan',
If you have cooked your ECU the only way to test is usually to replace with a known working unit and hope that any faults on your bike don't cook the unit!

If it is all "potted", as per shrimps,

sealed in that black stuff rather than butter then unless you have the necessary test rig you will not be able to diagnose the fault.

I believe the ECU are ~£400 a pop!!!

I have never dealt with Enfields, but my local motorcycle repairer used to be an authorised Enfield dealer, until Enfield required a 12 bike range in stock, plus spares as prescribed by them! He is also a vehicle electrician of 30+ years.
If you would care to be more specific about which wires "fractured"

on the ECU, I might be able to obtain a specific answer. Probably along with a few expletives about the owner!

Off to deal with a Morini!

My regards, Bill