Hi James
If you mean this stuff:
Paint Insulation - Insulating Paint Additive - Ceramic Paint Additive then no, never seen it before, but it sure does look expensive for 5litres worth @ £20 a pack.
The average sized double bedroom needs about 10litres of paint to do 4 walls and a ceiling with 2 coats of decent quality paint like dulux, so thas going to add £40 a room.
It "looks good" on the surface so to speak, but you might want to try just 1 pack and give it a shot somewhere thats easy to clean up if it doesnt come out good.
Please do let us know how you get on with it too, if it works out good, and gives a good finish with your painting, then I'm sure others wouldnt mind giving it a whirl.
Let us know if the paint finish feels any different, and how easy it goes on when mixed with the paint too.