Just to add my two penn'orth, we've used the Sanef (Liber-T) tag on our 4/4 for many years without any problems at all. The car has the usual heated windscreen and the tag is mounted centrally on the inside of the screen, just above the central "lift the dot". I decided to put it there to help remind me to detach the tag from its bracket and lock it in the glovebox when leaving the car. You can easily order more brackets from the Sanef website to use on your other cars, should you want to take a non-Morgan across the Channel.
