Why do they believe the ECU is broken?
Mainly because I’m an idiot!
The existing ECU was ‘cooked’ in an attempt to cure a P0306 misfire fault (according to this ‘fix’:-https://www.subaruoutback.org/threads/h6-cylinder-misfire-p0306-dead-cylinder . 429001/page-3#post-5882235.)
After cooking (which didn’t go well and melted the connector blocks!), I was able to reconnect it and the engine started and ran fine, but didn’t crank properly and reported other fault codes (mainly for connection/communication failures) .
All attempts to troubleshoot those faults just made things worse and I sent the ECU to a specialist for repair.
The board has been examined and found to have areas of delamination under some of the chip connections which cannot be repaired, so the only solution is to recover the coding (which can be achieved by direct connection to the relevant chips) and transfer it to a good. board, but apparently it has to be a board with the same part number for the firmware to be compatible.
If anyone can suggest another solution I would be very pleased!!
The 3.6R seems to be a bit of a unicorn in the UK and I can’t find any switches with 3.6R parts (or at least none with an ECU available).
Hope is dwindling but I’d really like to get the car back, it’s a great mix of power, comfort and usability that will be hard to replace. 
