It appears that I’ve installed the flue pipes upside-down! When you burn any wood a certain amount of creosote is produced, as I’ve found, which should then funnel down the flue pipes and back into the stove. To do this, the ‘male’ end of the tube above needs to be inserted into the ‘female’ end of the tube below it, not the other way up as I’ve done it. Simple common sense when you know and an easy (but stupid) mistake to make when you don’t. The clue was which end of the tube packaging the labels were on ie the tops, but I was thrown because I thought the bottom tube fitted over the wood burner’s outlet whereas it doesn’t, it goes inside it.
So I’ve now got to allow the fire to go out and the flue pipes to cool before removing them all, cleaning off the mess on the top of the wood burner and replacing them the other way up. Fortunately I haven’t got to worry about the dried black mess on the outside of the tubes, except for removing the excess to prevent it melting and running downwards again, because when they’re back, nobody will ever see them. It’s just the top of the stove itself that’ll need most attention and hopefully that won’t need too much effort to clean up so long as I do it soon – like tomorrow maybe? Bummer, I want to go flying tomorrow – so maybe do that while everything’s cooling down, eh?