Opening up under stairs - brick supporting wall above, What size of RSJ? -welded/bolted?

[Blue Nomad]

Help!
Anyone have experience knocking about stone terraced houses in South wales?
This is a common thing to do with these houses but i can find any details that are not behind paywall quotes, not ones where the above wall is load bearing.

Here's what i don't know and would like help with:

Is my drawing realistic with what has to happen? (Drawing to scale dots = 1foot)
My building experience is limited to timber structures - I'm assuming i need an RSJ if there are bricks above? not C24 (new bits shown in blue)

What dimensions of I beam do i need, 6"? I'm assuming it will rest on the solid dividing wall?
More importantly how much does it cost to get one made?
Are they commonly bolted together or is it cheaper to get it cut and welded in the 2 angles?
Who does this in south wales? No fabricator was specific - only about new build/knock through modifications or per m etc.
2 photos showing my plans and current layout.

Space is not abundant, I need freezer and WM in the kitchen, larder & worktop space - i.e. I don't want a central 4" pillar under top of the stairs.

I do intend to get pros in to do it but i'd like to know material costs and specifications before hand.

I hate asking for quotes before i am ready or can afford it-I feel it wastes their time.
Or the ever popular - 'you're clearly not trade sweetheart so i shall be dismissive and vague' kind of response
(despite probably having taught engineering and construction to their children or even them.)

Can i sit the beam under the stair treads adjacent or sistered to to the wooden central and edge stringers instead of resting them on it to keep some extra height on the diagonal? With solid plastered wall i can't see how the stairs are attached on the kitchen side - assuming they are not hung as you might nowadays. The stairs and layout are original and open into kitchen and there are fire doors on the bedrooms for fire regs.

I'm not interested in a 'make good and leave shiny' quote, i can re-plaster myself - doing some anyway- insetting wiring - currently plastic conduit everywhere.
I just want the first fix option as i have a shoestring budget. I just need to ensure structure is sound and structural building regs followed etc.
I've been told its fairly straightforward and can be done in a day, but i'd like some more opinions, i don't want to inadvertently invite in a bodger.

Any help on figuring out my options and breakdown of regs and costs would be really helpful.
Thanks in advance


(I also plan to open out the bricked up chimney just where the old coal range would have gone - (hearth is still there) to fit the oven (mostly) in it,
Anyone know how high the arch/lintel tends to be? I'm in Abercarn. id rather not cut random holes in the plaster to find out. Difficult to estimate from old photos of similar. -trying to avoid having to install a new lintels if its high enough - is there a minimum height needed above cookers?)

 

[cdbe]

You need to get this moved to the building section (I think you "report post" and the mods will move).

I can't quite fathom out what's going on, but if your plan is to remove most of the masonry wall below the first floor you would normally insert a straight steel at first floor level to support the remaining wall above. But there are cheaper alternatives such as removing the upper section of the wall as well and replacing it with a lightweight stud wall.