If the hot water is fine then you will probably have a 3 port valve and a cylinder thermostat?
yes there are what appears to be to thermistats on both the dwh
and the ch
would the ch thermistat be faulty
No, the central heating thermostat controls the temperature of the house, the cylinder stat controls the temperature of the water, but the boiler stat controls the temperature of the circulating water
So if the rads are too hot to touch then turn down the boiler stat (behind the front cover under the fire)