I got a couple of hours on this today, I hooked the scope up to the Diagnostic Socket pins 6 & 14 & started pulling ECU multiplugs off to see if I could get a CAN capture that looked normal - anyhow the car is now in pieces with every ECU I could find unplugged -

Steering Rack, Engine, ABS/ESP, Column Module, Airbag, Wiper Motor, Air Con, Parrot, Radio, Dash etc......
I'm up to the middle of the car now & still..........

no difference on the scope

Tried a CAN Gateway - the pattern looked more normal, but still had parrallel parabolics sloping down between messages, but I still couldn't get comm's with the Gateway itself or any other system apart from engine (the other systems aren't surprising as the Gateway needs coding in).

My thoughts on this was that because the Gateway wasn't in the loop due to not being coded - it was sat watching data packages going by without getting involved in the data stream - Is that likely??

Now it's largely in bits, my next step is to scope individual ECU's on the convenience / infotainment & powertrain buses (the dash is unplugged) & see what kind of activity is present on the individual buses.
I'm also going to go with looking at power supplies / earths.

Any pointers at my procedures would be appreciated - Cheers,

Jon.