Thank you Scotts90. The colours match and the socket was obvious when I pulled the plastic cover off this morning. There's also a 7.5 fuse with black and brown leads. Is that for the EGR too?
I may fit a diesel heater in the future (I certainly want to keep the option open if I can) so I want to keep the space underneath a cubby box as clear as possible with a view to having a wide hot air vent passing below the cubby box. I have already blanked off the EGR in the engine bay and I have removed the EGR ECU from the central seat. Most of the cables can be housed below the central base plate, but I assume I need to keep the TestBook socket accessible.