Yeah, heated windscreens have been an issue for a few. if I remember correctly each side is on a different fuse, so that's worth checking. Secondly, I recall that this can be related to battery condition. It seems like the system seems to shut down one side if the battery is low. I have a feeling that it might not differentiate between left and right hand drive vehicles though. At 4.5 years, the battery may be weak if it has had little use or has done a lot of short journeys in its lifetime.
B Max Titanium X 1.0 125 bhp in Magnetic with built in SatNav and rear sensors.