A warning is going to be useful at this point - one of your injectors has a sensor built in, it might be No. 1, on mine it is No. 2. This injector can be tested, but cannot be re-nozzled because the sensor gets damaged - I have been told this by several places including Bosch service centres. All the others can be tested and re-nozzled, but if the sensor injector is not spraying properly, or the sensor has given up the ghost, you will probably be looking at around £500 to replace that injector (may be less since yours is newer, mine is pretty obscure part number now). My advice therefore is to choose your tester wisely and make sure they are Bosch approved and familiar with this type of injector - there are some out there who only really do CDI injectors and even then some may not test them properly - an ultrasonically cleaned injector looks like new but doesn't demonstrate that anything useful was necessarily done to it!
To be honest at this stage since your main ECU has been checked, I would probably be looking at the fuel pump ECU.
As I said before when I had a sensor fail in the pump fuel was coming through but not at high enough pressure to open the injectors - looking at exploded diagrams of these kind of pumps I think I understand why:
The engine management system controls the injection quantity by moving a plunger in the fuel pump to control the volume of fuel in the central chamber. As the engine turns over the pump goes round (chain driven off the crankshaft) so will always push the fuel in the central chamber to whichever injector port is open at that stage in the cycle, so you always get fuel in the injector line. But when the engine management system has a problem instead of shutting the fuel solenoid it seems to just leave the central plunger in a position where the quantity of fuel to be pumped is not enough to build up the necessary pressure to open the injector nozzles (2 stage spring loaded - not controlled by electronic pulse like CDI injectors). Hence, fuel comes out of the lines and you can bleed the air out, but it doesn't spray out of even a properly working injector because it doesn't reach the 190bar (I think) to open the first stage, never mind the 400bar (I think) for the second stage.....
So it could be that if your main ECU is OK but it is still not possible to read any codes for the fuel injection system, maybe the pump ECU has a problem, or maybe there is an electrical problem between them, and maybe this is why it won't start when everything seems to be right otherwise. Like I say, mine did have communication and they picked up a sensor failure, I reckon other failures such as communication itself could manifest in the same symptoms.
Perhaps you need to look for someone who can test the pump output and/or hook the pump up directly to diagnostics and check it out?