Just in time hopefully?
I smelt that burning the last couple of cold mornings, twigged what was going on yesterday, so switched off the demister pronto!
On first sight, the fusebox and fuse looked fine, but when I pulled the fuse it has started to melt (pic attached). I haven't had a chance to check yet, but hopefully I've caught it before any real damage to the fusebox itself.
Checking back in the car's paperwork, the fusebox had already been replaced once in 2005 by Alfa (at 3yrs old) for this exact problem, but clearly they didn't go as far as sorting out the real source of the issue; surprise, surprise...
Anyway, the fuse is staying out so I don't forget and turn it on again by accident!