I had an SE do the calcs for the steels, but I'm confused as to what they mean.  He has specified 254 * 102 * 22 UB.  Whilst I understand a UB works for the inner steel, I don't see how you use a UB on the face brickwork side, or why it requires a UB as the load of the external face is much less as it's not supporting the roof or floor.

 

Does anyone have any advice on what steel design you would normally use for a ground floor 4.4m sliding door.  Estimators specified a Catnic https://condell-ltd.com/catnic-cx150-100-4800mm

 

And I understand how that works as it is shaped for a cavity tray to easily be fitted and the exterior brickwork to have the required weep vents, but two parallel UB lintels would not work like that.

25578 - White Cattery Lane, RG26 5TN.pdf

Ask the SE if there is anything you are unsure of.  It is what you pay them for.  A normal lintel is easier to deal with.  I have used the Hi Therm ones before and they give you the psi values which is useful for your SAP calcs.  Maybe some of your openings are too wide, so beams are the only way?

I agree with Mr Punter go back to the SE and ask them how the external leaf is supported. I just love a set of computer generated calculations which mean very little to the average builder and lack any "constructional" details which explain how the designed beam interacts with the building.