Thermostatic mixer taps

That looks like a wax pellet type, which is OK if the incoming water pressure and temperature aren't likely to change suddenly. If you're going over to France, it might be worth looking over there. The shower-only version of this are about 1/3rd of the price over there that they are here.

These don't work very well with instant water heaters (combi or multipoint), where for the shower, you really need a fast acting mixer which can also cope with mismatched/varying pressure, but that's significantly more expensive, needless to say.

Note this particular one needs 1 bar pressure (i.e. the tank needs to be 33 feet above the tap, if it's tank-fed and not pumped). There are taps which can operate at 0.3 bar (10 foot head), although I don't know about thermostatic ones, and the shower wouldn't be up to much at 0.3 bar anyway.