It will cost a lot more than the original estimates etc, as these things always do!

ECOSNIGE
Have a test/long think about underfloor heating before you go too far with it. We have it in half the house (En-suites, bathroom, kitchen, utlities and garage etc) and it is very different to having radiators. Its much slower to heat up and cool down etc.

The electic underfloor heatin in the kitchen is better (well quicker) than the hot water based stuff in the other rooms though