Are you looking to install it or repair an existing one?
Any normal builder can install an electric underfloor heating unit. It's not that expensive, if you're having a re-furb done already. We had our kitchen & bathroom done recently and our builders installed it, it was about 300 pounds per room, plus maybe 200 to fit it.(we were having a complete new floor anyway, so it was easy to fit)
Let me know if you want details of the builder who did it.
It does cost a bit to run, but having warm tiles in the morning is really quite lovely