TD6 Air Suspension problem

I'm having a bit of a nightmare with the air suspension on my Range Rover L322 TD6.
Two weeks ago i got the air suspension / hdc inactive message on the dash and the next morning it had dropped to the deck.
I'm fortunate in having a diagnostics code reader and the only fault it was showing was code 50 Can Bus Fault.
I've since checked all the air bags for leaks, the ride height sensors individually and the pump, they all are fine.
On start up the pump runs for a around a minute and then cuts out with a hiss, as if back pressure is cutting it out / turning it off.
The suspension lock button light is constantly lit and no matter what i do it wont go off and i cant get the can bus error to clear either, i think this is somehow preventing the suspension from lifting.
I've a gut feeling that the issue is something electrical rather than mechanical.
Has anyone experienced anything similar or anything else to check / possible solutions?
Thanks for any help in advance.
Regards
Stewart

I think the "Front left height sensor fault" might be a clue!!!

Thanks for the reply,
The front left height sensor is definitely working, the fault was caused by me testing it was working by unplugging it. I've already tried swapping the sensors at the front over, with no change and the live data on the computer shows the height change as you move the plastic arm up and down.
As i unplugged each height sensor the machine immediately showed it as a fault and then cleared when it was plugged back in. I'm 100% sure that each of the height sensors are operating correctly.
The only code currently showing is the 50 Can Bus Error.
Sorry for any confusion the picture caused.
Regards
Stewart

Ok, fair do's, just realised it sounded a bit sarcastic, wasn't meant like that.
@Saint.V8 has delved into the various communications buses on these so he might be able to help.

Do you still have the Hadlight Leveling ECU connected?

This is well known for dragging the CAN down.