Go into Car and then Status and there is a Start Stop icon - press that and it takes you to a screen that tells you that start stop is available, or why it isn't.

Thanks for the tip Andy. The stop start has been working lovely this week so I think it was just user error on part. It is great that you can press a few buttons to see if the stop start will work or not. Pity it is not displayed on the maxidot though. That would be better since I don't really want to leave the vehicle data screen on all the time if I fancy seeing the info.