Insulating concrete slab

[steve_s]

Look up aerogel insulation. It's extremely thin but has very good thermal efficency. A layer of this then a layer of ply would make a considerable difference. Only issue is its pretty expensive as far as insulation goes.

OMG that is expensive £170 for 1200x1200 (4x4 in old money) 10mm thick

 

[roryswfc]

Fit for purpose though. Think it is the equivalent of about 100 celotex

 

[Pipe Dreamer]

OMG that is expensive £170 for 1200x1200 (4x4 in old money) 10mm thick

That's about the same as the first quote we hadfor rebuilding the shole garage ... and that was 3 times to much
maybe I'll just run 5 space heaters instead.

In all seriousness, thanks for all the input.