Hi Peter, I am now in my third year with the Land Rover T4 (was called testbook). & I can honestly say every time the warning light was on, there were codes stored.
I have never had a problem with no front codes stored. There was a problem with a few vehicles, which would throw up an error code (NOT ecu stored), which had to be ignored, due to software error on the T4, but I think is now fixed, as the latest CD has gone back over older models & updated the software. This didn't effect the diagnosis of the vehicle, just annoying.
There will always be minor issues with T4, but at least you can usually just put the older CD in & give that a try, as most errors are just a software re-write mess up, & OK on older discs.
I hope that Autodiagnos take on board your problems & sort them out, not just say that "they're all like that".