They are only £15.99 at Aldi, Stove fan that is. We have one It doesn't rattle.
We have a villager stove, if it is shut it will go out by morning, open too much sweating buckets in the back, and burnt out by morning, fine line, however I haven't ever see the stove glow red, though hot enough to open all doors in winter.
As for gobbing. I am not a plumber, not used google, I am using assumption/ logic (tin hat on), put a cap on flue/chimney, close all vents, light the smoke pellet, put the smoke pellet in stove, shut door, stand back and look for smoke coming out ?
It may be worth getting a candle, close up the stove, leave the Flue/chimney in place, and open. Go around the stove with the candle, the flame of the candle will be drawn towards the draft. Go around all the joints, start at the bottom.
I hope this helps.
Just my opinion you understand, this is what I would do.