Help!: Floor preparation for limestone floor

[Team Webb]

Hi
I am renovating a 1903 detached house, we have had a wall removed between two rooms to crate a L shaped space that will be a kitchen diner. this now makes a rather complicated floor structure that has:

1) a small section of suspended wooden floor, 3m x 1.3m that joins directly to
2)an area of concrete (the original kitchen floor of the house) this is fairly level but has some adhesive left over from where the lino was stuck directly onto it. I would guess it also has no damproof membrane as it is original to the house (the house has a slate damp-course)
3) we then had a wall removed that leads to the area we are now going to put the kitchen in. This has a gap where the wall was and joins to ½ concrete where a fireplace area was constructed (this is ~4 mm above the level of the concrete in the other room) and the rest of the join and room is suspended wooden floor. The room is 3m by 4.3 m
I have removed the floorboards as I had to replace a number of rotten joists (the under-floor ventilation was poor and they had leaking washing machines and doorways next to them).
The difference in height from the main concrete floor and the joists is 22mm.
Reading the boards I think my plan of action is as follows:

1. 22mm WBP on the joists (after insulating beneath them with rockwool held in place by netting) screwed down every 40cm with 2-3 mm expansion gaps.
2. Cover whole area with a decoupling membrane
3. Tile with a flexible tile adhesive on wooden area and with normal adhesive over concrete

So the questions are

1. Is this completely wrong? Or partially wrong and if so which bits
2. Why does it seem I can only get 25 mm WBP? Where can I get 22 mm?
3. Does the Concrete need anything doing to it? How can I get the old adhesive off to make it slightly more level (it is only a mm or so proud)
4. Can I use goldscrews on the plywood or will these rust?
5. Will I have to fit noggins if so what spacing (I can recall the gaps between the joists at the moment but they would be typical of old buildings)
6. Shall I fill the gap where the wall was with concrete up to the level of the old floor and chip the bits of the old fire place off to make it same level (only the edges and a few lumps are proud by a couple of mm)

Sorry that was a lot of text but I wanted to try and give as much info as I could. I hope it makes sense. Any suggestions would be most welcome.

[GirlRacerRed]

bumpety bump

any ideas people?