Baxi bermuda downstairs, what would I find upstairs?

[smp50]

I have an old baxi bermuda system sitting in the original chimney breast downstairs (with a small section of false wall added on the side to accommodate pipes).

Directly above is a bedroom through which the chimney breast passes. There's an area of concrete around the chimney breast on the floor, flush with the floorboards, which I presume implies there was once a working fireplace there. Indeed, there's a small vent in the wall through which I can feel a draught, so the chimney is still there behind it.

My question is, if I wanted to knock out the wall upstairs and investigate the fireplace cavity, could it have any affect on the flue of the baxi, or will that run through a completely separate chamber?

Also, in general, in this 1930's ex-LA house, will it likely just be a small, dirty brick hole there, not big enough to put some small shelves in or anything nice like that?

Thanks

 

[Nige F]

Also, in general, in this 1930's ex-LA house, will it likely just be a small, dirty brick hole there,
Thanks

Very likely

 

[onecog]

It will be a seperate flue.

 

[OwainDIYer]

It should be a separate flue.