I think your ECU is fine. You have some fault code that is keeping the system from operating.
You have a few choices. You can temporarily bypass the ECU by simply unplugging it. That will hold the system at the current inflation. You can safely drive it as long as it has not gone to the bumpstops.
Inflate it manually: You can make a small pigtail with 4 wires. strip both ends about 10mm. gang all 4 on one end. The remaining wires go into the (unplugged) AMP plug in the following manner...
Connect sockets 1,8, to start the pump. It will shut off when full. Connect pin 1 and 26 to inflate. Connect 1 and 9 to deflate. The air bladders are as follows: LF 10, LR 11, RF 27, RR 28. So to add air to the RF for example, you connect pins 1,26, and 27. To let air out of the RF you would connect pins 1,9, and 27.
I know it sounds confusing but after you do it successfully, it all becomes simple and clear.
Finally, you'll want to visit Storey Wilson's site
where he offers instructions to make a com cable which will allow you to read and clear codes, set min and max height, and otherwise live harmoniously with your EAS system.
One note...the cable end he refers to (the 5 pin Rover end) is unavailable. If you are super lucky maybe you can scrounge one somehow, but it may be best to simply hack off the plug and replace it with something else that is easier to source. Autosparks.co.uk has some other choices for you that are similar.