Martin wrote:

I'm fitting an extractor fan in our kitchen and have a little problem
with the hole it will extract through. To make the hole I hired a diamond
core cutting tool from HSS and used the largest bit about 6". Having bought
the extractor and sleeve the hole needs to be slightly bigger to accommodate
the sleeve. Any advise on how I can neatly increase the size of the hole.
For example is there such a drill bit that effetely files the brick away.

Use a scutch chisel with hammer, to gently and neatly nibble away the
required brickwork. Wonderful tools.

David