Sensor to control multiple zones

I have 3 zones. 1 underfloor and 2 radiators. I work from home. During week (daytime) I have the office area (loft) on but the rest of the house off, which is fine, but evenings, weekends etc. I want to heat the whole house. Problem is the heat from the rest of the house rises to the loft meaning the loft rads and towel rails don't come on. Towels in loft don't dry and downstairs heating struggles and the boiler is burning longer than it needs to. For weekends it would be much simpler if the whole house including the loft just ran off the main house thermostat. Right now all i can do is crank the loft thermostat up to ludicrous for an hour morning and night to push the heat through which is just wasteful.