How do I clean this? I haven't cleaned the insert or chimney before. I looked at the instructions and it says to remove the fake brickwork at the back of the stove, but do I need to do that? Also, what's the best way to clean the top of the insert - some bits of pellets have fallen into the slats. Appreciate your help and sorry if the questions are basic, but I tried to google the forum and didn't find the answer.