Hi everyone!
On a legal note, if the garage has done something, they clearly have as you presumably drove it in and now it won't start, to cause this damage, then the responsibility will be on them to put you back in the position you were when you took your vehicle to them.
Did they do some electric welding, without disconnecting the battery, to be able melt the ECU?
Or what other manner have they managed to short out some electrical circuits, without fuses and other protection devices doing their jobs, in order to cause that level of damage - "inside the ECU had melted"!!
As Picasso says, there are several ECU's on them, but I guess it must be the main one to have the problem with the immobiliser, and not be able to read anything from the OBD port, which is pretty jolly serious.
Has the ECU actually melted, have you seen this?
I do not know, so this is a question for anyone out there, if a new ECU is plugged in, will it know any fault codes on a "new" to it vehicle?
I'm guessing now, but will it read the normal parameters from the car, and report anything "off schedule"?
But would a new ECU need programming to the car?
Beyond my knowledge and skill set that one!
Do not be too nice about this, it can bite you on the backside, if you tow it away, and they try to wash their hands of it.