Hi! I want to fit a mixer shower in place of existing mixer taps. The taps work OK, I just want to up-date. The hot water is from a Vokera 20-80 RS Flowmatic, which I'm told is not a fully modulating combi, but a step modulating one. Is that so? Mira (the best) say none of their units are suitable for step modulated combi boilers. Is there a way round this please, without going to an electric shower?