Some mono-bloc taps come with flexi's because the tap inlets are close together. If your replacing like-for-like they should fit OK but make sure you change the fibre washers for new one's. It is easy if you have the right tools.
Danfoss Randall do a underfloor heating control for use with combi's have a look here :- http://www.heatingcontrolsonline.co.uk/danfoss-randall-fhvr-p-246.html