I run the heating last year at 50 but, due to a boiler requiring smaller rads than a heatpump, I felt the house wa on the cooler side on the real cold days. However for this year I have fitted that weather compensation kit and will let the boiler do its own stuff – cooler flow or hotter flow. I will report back over the winter.
As for hot water I have kept it set to 60c. The recomendation is to set it at 60 -65c to kill unwanted bacteria like Legionella!!