Go back into the the setup and select cancel/reset.
as the speed warning can be setup 2 different ways depending on if you have the ACC or Not.
The Manual is a bit unclear, but it does say to go in the setup and and use the OK/Reset button on the ACC.
Just have to have a play.
Found it!!! There are, apparently, two totally different, and independent, types of speed warnings. The one that I had problems with is "Winter Tyres - Speed Limit"
So, (obviously!!!), to reset the speed warning, I had to scroll to the bottom of the TYRE section!
Thanks for your comments.