"However, the main reasons the satnavs cause problems is because it can take months for map updates from local councils to make their way onto the gadgets."
And the rest... What about those who bought the satnav, and then don't sign up (with ££) for a subscription which provides updates?
Anyone that follows a satnav into a river, over a cliff, or down a footpath should be hit with an "Undue care and attention" conviction. A few of those and it's bye bye licence, so they'll either learn to look where they a bl**dy well going, or be removed from our roads. The latter would seem to be for the common good.