[rab60bit]

The radio tuner multiplug is very vulnerable to the water that often accumulates in the wheel well *see numerous posts 'water in the boot'
For a start, remove/inspect/clean the tuner socket and likewise the multiplug. Add a bit of contact grease to every pin and re-assemble; switch on and you might be lucky, hey presto a working screen. If not it's likely the tuner is goosed with corrosion - anything in the region of the lower end will have been flooded at some time or other. Look for a used Rover tuner replacement or better still try to source a BMW BM24 or BM54 tuner, both superior radio quality plus plug/play......and find the water leaks, they are a real bug..r!