Removal of Gas Fir- Is brick arch Lintel safe?

[Cell01]

Hi, Had a gas fire removed and am looking to get rid of the old firebox and extra brickwork that's been added into the original hole so I can put a (purely decorative) cast iron fireplace in. It sticks out at the moment so needs to be removed. I've chipped back the plaster to look for the lintel so I know how much I can safely remove, and there doesn't appear to be a lintel as such, just a shallow arch of 'side on' bricks. It appears pretty obvious that the two rows of bricks beneath it are added as part of the newer fire conversion, but there also appears to be a 'mini' lintel that sits on the two uprights of the firebox. Have read somewhere that this is a 'throat' that just directs fumes, but just making sure - It certainly doesn't extend across the width of the fireplace. I'm really just a bit concerned that the original 'arch way' doesn't look that robust as it's rather shallow. Should I add a lintel underneath it to be on the safe side or trust the physics of the arch? Terrified of 'bringing the house down' as it were!

Any advice Much appreciated!

[welsh brickie]

I have replaced more than a few of these old ranges,The arch is usually safe,There is usually a metal band underneath the arch to reinforce the arch.If not and you are unsure of the stability seek proffesional advice