Not related to the actual query, but I thought I would stick a little note in here in case anyone has the same problem.....
THIS IS TRUE... NO B.S!
If you fit aftermarket bulbs into the tail lights of your Astra Coupe (especially LEDs!), then the Cruise Control will fail to operate. Pressing Cruise Control will not activate the system and the only way to resume "normal operation" is to replace the bulbs again with "like-for-like". I don't think this would affect people putting in after-market rear light clusters, but then again..... It must have something to do with the change in voltage, but why it affects the Cruise Control, I have absolutely no idea.
All I know is that after a weekend of p1ssin' about trying to fix it and retracing my diagnostics and steps... I wasn't best pleased when I realised what it was that had caused the problem....
Regards,
John