again thank you for your replies. yes Steve you were right the communication errors were being caused by the fault.
Sorted, behind the heads the transmission loom had a wiring loom clip off. The loom was sitting against the egr pipe, a tiny part of the insulation on a wire had melted allowing it to occasionally earth out. Took a fair while to rectify as access was an issue. I really should have found this faster! but hey ho its sorted now.
Thank you to all took the time to reply i really appreciate all help
I agree that CAN shorted to an EGR pipe should bring about a short to zero volts and pull the CAN Bus down to ground.
Reading through, it may not have been a CAN wire shorted to the EGR pipe but wiring responsible for the operation or position of Transmission Range change.
It would appear once this fault occurred (so flagging P0902) that the relevant ECU responsible for this code produced the behavioral characteristics on the CAN line in the original post
Yes sorry I should have been more clear, it wasn't a Can line shorting out.
I've since taken the car on a few test drives probably totalling 20 miles. I still have the strange irregularities in the Can H/Can L yet I have no communication faults or fault codes. So am a little confused on that aspect
I had worse on a zafira a still no faultcodes, reason, messages are retransmitted so fast, that there is no reason to flag comm fault just for 1 can message.