Restoring chimney breast opening. Issues with original brickwork?

[Yardstick]

Looking to reinstate the original builders opening in a ground floor chimney breast. Concrete lintel to be installed as there’s no clear arch/lintel/support in the chimney breast at the moment. A simple enough job / no issues here.

The brickwork generally is in a bit of a state though. Previous owners have at various points installed a gas fire and knocked out sections of bricks to create small alcoves in the brickwork (see first picture)

There’s a change in brickwork pattern at the alcoves. Below the bricks are all in the same orientation - they aren’t toothed together

Key question for me is whether this is cause for concern from a structural standpoint. It’s not something I’ve seen before, hence the concern

Is it something I should be looking to resolve ahead of plastering? Or it sound enough and will just be a case of filling the alcoves?

 

[blup]

Whats it like inside, can you stick a camera phone in for a pic.

Blup

 

[Yardstick]

Whats it like inside, can you stick a camera phone in for a pic.

Blup

Cheers. There’s a lining in there by the looks (see below) so not a huge help I’m afraid in terms of brickwork.

Camera here angled towards where rear and right hand jamb meet

 

[blup]

The stretcher only bonded brickwork higher up suggests nothing being supported other than the wall above which the lintel would address. So logically any brickwork below can be removed. But depending on the design of the flue internally there may be other parts of the wall supporting it.

Blup