Hopefully this post will assist others that may be getting an error H6 on their Daewoo washing machine. Mine is model DWD-F1021 but it may also apply to many others, including 1022/1023/F1221/1222/1223 which share the same instruction manual.
A quick Bing Search for daewoo washing h6 showed a number of options, including blocked pipe or broken heater. The drainage pipe and pump were OK and a quick test of a cold wash went through without error, so that suggested that it was related to the heater.
I popped the back panel off the washer and sure enough, one of the wires for the heater had come loose. It was a simple push-on connecter so the fix was simple.
Not sure how much an engineer call-out would have been – cheaper than a new washing machine no doubt, but still very expensive. The best news though was that Miranda gave me a sticker of a tiger as a reward which I am now sporting on the back of my hand. Happy days!