With radiators in the loft rooms, the temperature overshoots the 'set' value because the Neostats shut of at the set point while the radiator continues to heat the room.
The Neostat could (hopefully) be modified to learn the size of the overshoot and compensate by shutting off earlier, i.e. below the set temp, and allowing the overshoot heat to warm the room to completion.
The learning process should be similar to that required for the pre-heat functionality and would need to be continually engaged since the thermal performance of rooms may change with external temperature and weather conditions.
Overshoot may not be avoidable in a small room with a large radiator where the overshoot adds more heat than the actual heating time. In this case I guess a minimum 'on' time may be required to avoid the overshoot compensation completely disabling the Neostat from operation (see https://feedback.heatmiser.com/suggestions/132868/minimum-run-time-setting).