Chimney breast removal

can I get a builder to remove the bottom of a disused fire place.
We want an annex in our cellar and the bottom of the chimney/fire place sticks out into the ceiling area of what we want to use and will look odd if just covered up.
The mortar has cracked and the bricks are loose sat on top of a concrete slab.

The pipe going through the stack is an old gas pipe which is being removed.
Hope someone can help.