It is not entirely clear from your description but presumably your underfloor heating is in the form of hot water pipes fed from the boiler which also feeds the upstairs radiators. OG's reply is correct in that as a single system a balance needs to be created between upstairs and downstairs - turn down the valves out of the radiators so everything heats up equally. But I would expect the underfloor heating to take more flow than the radiators but this depends on the pipe size and whether they are throttled and to what degree. ladybirder's implication is also correct in that it might be better operated as two separate systems, but that should not be necessary. However, underfloor heating is different in that for comfort reasons it is run at a lower temperature and the reaction time is therefore longer and, ideally, this means running it continuously. If you have rugs or carpets on the floor then you are actually insulating the room from the heat. The most efficient way to benefit from quick transfer of the heat in the floor is by tiling the floor, parquet is a mild insulator. In winter the UK is a cold place and to heat a dwelling intermittently (e.g. only morning and afternoon) will not keep it warm, especially if underfloor heating is below a parquet or carpet. No matter which form of central heating you use, intermittent heating is inefficient and also leads to problems such as condensation/dampness.