Ive looked into this further.
It seems that if you go on settings > Drive assist and hit the notification tab you should have options for "excess speed caution options", "speed limit change notification"
If you change the speed limit notification slider to off, it will come on again when you start the vehicle. Instead, leave it permanently on and change the "excess speed caution options" to "visual".
That should leave the system on but it shouldnt give you an annoying bong all the time. It seems to have worked in the States but lets see if it works here in the UK