Floor Insulation

I spent some of yesterday and a bit of today laying floor insulation in the house. It is rigid foam sheets 5cm thick and about 8 foot by 4 foot. It is foil backed on both sides. The time consumng bit is cutting it to fit around the water and heating pipes that are laid on the floor. I've done what Kingspan recommend - and used 20mm thick stuff around the edge of the outside walls (on the inside of course) This is cut 4 inches high. Most people - including the builders merchant and the floor screed man tell me that no-one hardly bothers doing this - but it's the only chance I'll get to do it right so I might as well.
I've still got about 2 fifts of the house to do - most of the fiddly bits are done apart form the utility room which is full of pipes so there isn't much floor space left to insulate!