I'm not 100% on the construction as it was like this when we moved in.
Does that side wall of the bay drop down to ground level or is it supported below?
So under that bed room bay is a pillar this was put in for the porch extension, I believe there is a lintel above the pillar. Although I can't be certain what its made of Unfortunately
Is there a lintel above the ground floor bay window?
Sorry not sure but that part of the house is original with a new double glazed window
Are there any disruptions in the bay bedroom floorboards?
Only thing I would say is there's alot of creaking in the bedroom, but without pulling up the carpet not sure.
Looking up from inside the ground floor bay is the ceiling flat and level?
Yes there no cracks and looks good. See attached.
Can't really answer the questions fully as I just don't know
so sorry about that.
The cube like form on the roof, is external to the original floor plan of the house, there would have been a wall and door into the lounge originally.