I am currently installing my kitchen. It is a Edwardian terrace (i.e. looks
Victorian). Unusually, the floor construction is suspended wooden on the
same level as the principal rooms. This is bad, because I want a slate
floor, which (to my mind) implies some sort of heating to take the edge off
the cold floor. (Space heating by radiators).

So, what is the minimum thickness I could make a slate floor complete with
underfloor heating, so I don't get too much of a step up from the back room?
The floorboards are currently layed with hardboard. It took me ten minutes
to remove a square 25cm by 25cm, it is so well affixed. I don't fancy
removing any more of it.

Alternatively, should I bite the bullet, go for a substantial step up and
install wet underfloor and insulation to replace the radiators?

Christian.