Heatmiser deals with the control side of the heating, not the manifold and plumbing side. When the thermostat calls for heat, you will see the flame icon. If the Heatmiser Wiring Centre responds, you will see zone lights responding. The boiler enable should come on. That means that the control side is working fine.
If after this happens, if the floor continues to warm when the zones are switched off, it would suggest that the water that is flowing through the pipework has been set to high. Therefore it needs turning down on the manifold side. As the water temperature has not controlled by us, you may need a heating engineer or a plumber out to balance your underfloor heating system.
Just also be aware that after the system has been balanced it could still take a long time for the heating in the room to reduce due to time that it takes to cool the system down.