Robbie39

I am installing a cassette stove on a wall with an external chimney. The builders opening can't be widened enough to accommodate the stove so I will put it n in front of the opening and built a false chimney breast. Some questions, 1 should I block up the old opening with blockwork. 2 what should I use for the stove to liner connection. Do I just use ordinary stove pipe or twin wall or? 3 I will make the breast out of metal studs and class 1 board. Do I need to cover the ceiling and back wall ( brick and plaster) that will be inside the breast with the board also? Thank you All replies appreciated