Compression strength of (floor) insulation

I was not sure what insulation to select for under the screed floor in the living room. The thickness needed to be somewhere between 250 and 300mm, and I had lots of 200mm white EPS70 board I did not know what to do with. For the flooring in the old kitchen and extension, Floormate XPS300 was used, which is not cheap, not off the shelf for most building merchants and probably OTT unless I want to turn the house into a storage facility and drive around with a forklift.
Anyway, a quick collate of information from some specification sheets I arrive at:

	lambda	σ(inst)	σ(long term)	remarks
	W/mK	kPa	kPa
EPS70	0.031	70	30	guesstimated σ(long term) from other EPS products
XPS300	0.033	300	130
Compacfoam200	0.087	2560	1910
Celotex XR4000	0.022	140	60	guesstimated σ(long term)

Of course this has to take the weight of the screed as well. Assuming a density of 2.5(x10^3 kg/m3), 100mm screed weighs 250 kg/m2 or exerts a pressure of 2.5 kPa. So despite me worrying, EPS70 is absolutely fine for normal floors, which should have a 500 kg/m2 rating. Although EPS70 is strong, it is not very good with point loads, you can make permanent dents by poking it with your finger. Although the top screed should spread the load evenly, 80mm Celotex was used for the top layer. It is stronger, has foil backings on top and bottom which acts as a vapour barrier and is good for clipping on the UFH pipes, and the low lambda brings down the U value even further. The final lay-up has a U of  0.1 W/m2K, which should be good enough for (almost) anybody.

BTW: I am not sure about the relevance, but the whole lay-up of floor and screed should just about float.