Sorry I didn't make it very clear - yes this is the door mirrors and not the interior and vanity mirrors
The horn has also just stopped working and now the mirrors no longer get hot so I think they must be on the same circuit and a fuse has blown but the fues panel cover legend shows the mirrors and washers as having their own fuse and there is no fuse listed for the horn?????
Looks like our wiring is a bit different to what it should be!