Rear fog lights not working

[njk71]

Hi,
My wife has a MK8 High Top Ford Transit coffee van that has just failed its mot with a rear fog light fault. When you put the fogs on the offside rear fog lamp flashes on for a second then goes out and a fog light fault message appears on the dash. The nr side lamp doesn't come on at all during this.
I unplugged both rear light clusters and the fault still came up when the fog light button was pressed - I can't seem to find a fuse location for the rear fogs - does it have its own dedicated fuse?
Any ideas/suggestions would be well recieved.