Outbuilding floor on top of concrete.. advise please :-)

Hi all,

Just wondering if anyone can advise me before I buy the materials if this will work:

I've just finished building an outbuilding, the windows and doors have gone in and it's pretty watertight, but I've now come to the hurdle of the floor inside, at the moment its just the concrete base (room size 5.8 x 3.4). Everything is on a budget and this isn't a dwelling place, but I do want to use Jabfloor 100mm and then tongue and groove 18mm chipboard before the floor. So it was going to go like this from top to bottom:

Floor (laminate flooring)
18mm Chipboard Flooring
DPM layer
Jabfloor
DPM layer
Concrete base

Questions:

If I wanted to raise the floor by another 50mm, does anyone see the problem with me using 50mm normal polystyrene sheets before I do any of the above just to raise it up 50mm before the first DPM?

Do I need to put wooden bracing and a 100mm batten frame work so I can fix the 18mm chipboard down? or will it be ok to sit directly onto the jabfloor?

I apologise if I've come across naive, but am merely looking for the solution with what I have above to work for my outbuilding so it just retains some warmth! Thank you for the help!!