thankyou. researching now. I'm wondering if a failed controller would throw an error on all 6 glow plugs though. I'm just seeing a fault code on cylinder 1.

Also researching batteries to work out if there is a problem there that is causing a little flurry of errors that are remaining:

Particle filter system (004667)
Glow plug Cylinder 1 (004212)
Fuel filter heater control (004B1C)
Computer CCC Message Failure (00E18F)

While driving on the highway the battery voltage was around 14.1-14.2V. This morning before starting I noted the battery was at 12.4V, then immediately 14.9V after starting. (Then I assume drops to low 14s after driving a while?)

The car is otherwise running great. Starts first time, every time, no rough idling at any stage.