The one thing to remember with any heat pump is that the
flow temperature is critical to getting a good SCOP (Seasonal Coefficient Of Performance or efficiency in other words) i.e. the lower the flow temperature the better the SCOP and the only way of finding the best (lowest) heat curve (both level and slope) for your particular system and home combination is by trial and error and the home owner is best placed to do this. While your installer will set it up initially, in a lot of cases he/she will set it up in such a way that they are not called back because of a cold house resulting in the flow temperatures being not optimal (too high). Unfortunately, most home owners find this out only when their esb bills arrive.
The tweaking of the heat curve is essential to determining the correct flow temperatures for different weather conditions. Using a heat curve and 3rd party indoor sensors for zone control is like driving a car with a foot on the accelerator and the brake at the same time i.e. two controlers competing against each other and will result generally in a poorer SCOP and therefore higher bills.
So
@Zenith63, if you are happy with your SCOP (low bills) and are comfortable then my advice is to leave well enough alone and don't add any zone controllers (except maybe in zones prone to high solar gain for example but then only use them as temperature limiters)