Sparkie

Hi to all. I've only ever browsed this sight until now.
After many years shelling out hard earned cash on range rovers I bought a 2011 q7 3.0tdi 18 months ago for some trouble free motoring! All has been well until a random fault with not starting.
Iam looking for any help as the car has been in the garage for 3 weeks now!
Initially the break down guy told me I had 6 injector faults so I was taken home. The following morning it started for a minute (lumpy) then cut out. Then no start. I then changed the fuel filter and it started first time smoothly. Then it started to fire on 3 clyinders. Plugged her in and now I have 3 injector faults!
So off to the specialist who came highly recommended. They checked injectors wiring etc and blamed the ECU. Sent it away and was told it had water damage. Once repaired plugged her back in and back to 6 injector faults and a performance fault..... ECU now back at the repairers to have it checked. I've a reasonable knowledge of cars And get there eventually..
Iam torn between trusting the ECU repairers and the garage diagnostics. I don't want to shell out more cash on a new one to find out it's not even that!
Any help would be greatly appreciated