Heater fan works intermittently - like loose connection

It is a loose connection.

Look in the passenger footwell, under the dash. The fat red wire going to the fan, will be loose at the fan-end. Jiggle it about, and you should be able to get it working. Mine was fine once I'd duct-taped it inplace.

Thanks Nom, that was exactly it. very easy job - I wish they were all like that!

Instead of just putting the plug back I cracked some of the plastic shielding off around the end where it was 'burnt' and brittle then gently crimped the connecter for a tighter fit before putting it back.

The way the plastic was scorched makes me wonder if it was a fire hazard??

It probably is a fire hazard :)