My mate had a genius idea to the dormer with just 4x2" ceiling joists under a couple of alcove areas (main floor is 8x2").
Turns out there is just room to run a 6x2" C24 (red in the above picture) right through onto the wall plate at the top on both sides.
Left side we can even sit that in an internal brick wall.
Right side we can bolt onto the first 8x2 floor joist.
Then we'll run new 4x2 half span floor joists bewteen the centre wall and this beam.
End result - but by rough calculations, each alcove should be good for 400-450kg of total load on the left and similar on the right - and that is without the ceiling joists contributing anything. Yes I am mindful of the load on the right 8x2" floor joist but that only taking about 100-150kg of the load.
That was a good result - but I do need some longer 6x2" to reach so that will have to wait until next week.