I do actually know that I am really annoying when I spot things like this but I just can't help it! The first cottage is the largest and probably has several rooms which would each have a fire and an associated chimney stack and pot but this only has one stack with two pots and the smaller cottage next door has two stacks and four pots. This is all turning out really well though. 

I'm guilty as charged!  I think the problem arose because there wasn't enough planning in the design of the buildings.  I think that, when I started them, I was in a hurry to see something emerge, and I didn't plan them very carefully.  Another detail that I didn't get right was the way the slate roofs should fully suround the chimney stacks, and comfortably overlap the barge boards.  I shall try and correct some of the detail, even though I take a broad brush approach a lot of the time.