When I laid stone tiles in my hallway and kitchen a couple of years ago I laid loose cable UFH, and I'd use that again as opposed to the ready made mats. It gives greater flexibility in awkward shaped areas. If you go down that route use twin conductor heating cable, then you don't have to bring the tail end back to the beginning to complete an electrical circuit.
I laid the cable onto Dukkaboard insulation board and then levelling screeded over the top before tiling in the usual manner with a notched trowel. The levelling screed prevents any possible accidents with the tiling trowel nicking the cable.

Both systems work fine although we rarely use them. We currently use wet radiators in both areas. I installed them because it was a cheap future proofing job when our biomass boiler breathes it's last. I then have the option of going all electric in those areas, plus being resistive heating I can link it to my solar PV production via a power diverter.

Or cork https://www.wood2u.co.uk/engineered-wood-flooring/by-effect/cork.html

It is a wet room.

Posted By: WillInAberdeenWe laid vinyl on woodfibre insulation board, but an unseen leak under the cistern allowed water to wick right the way under the vinyl across the room. Everything was totally minging when we found out and lifted it all. We replaced it using inorganic insulation (marmox) with tiles bonded down on it, to eliminate wicking routes, and will never use vinyl in bathrooms again.

I don't quite understand the description. Vinyl directly on woodfibre? What provides the rigidity? Cistern, what cistern? Why is a leaking cistern the problem of the floor construction? Especially of the surface layer?

I do not understand the contribution of the vinyl to this story at all? Why are tiles better?

Thanks for replies so far.

A tiled floor is a done deal with UFH pretty much essential to avoid a sad face each winter morning. As well as warming the floor the UFH is to take the chill off the bathroom so pretty much essential even if moving to a covering other than tiles.

Was hoping to identify and lemon cabling/controller systems that needed avoiding. Anyone used the Klima matting that Screwfix sell?

Posted By: WillInAberdeenBecause

tiles eliminate wicking routes

No, it's not the tiles that eliminate the wicking route, it's the gluing down. Our wetroom has a proper contract-vinyl floor (as used in hospitals) glued down and wrapped up the walls. Installed by a contract floor fitter. Not that we have a cistern where it can flood under the vinyl anyway. But water falling on the floor stays on top of the floor until it reaches the drain. Water falling alongside the floor will drain down onto the concrete slab, not sideways under the vinyl floor, I believe.

The woodfibre insulation board that you mentioned was actually underlay, no? And it specifically says: "Not recommended for use on underfloor heating", so not really relevant here. Or is there more than one prduct that shows up on google

Bit late in the day but I put the Klima matting down with no problems and works well. Needed a flexible glue??. Thats more than can be said for the controller which I just cannot get to work on the thermostat so use the 10 min on followed by 10 min off programme. No complaints from better half so now wonder why I bothered with a thermostat.