Ive been using the IR Air to control a central air con unit along with motorised dampers for each room, I fully control the ac unit and dampers from IRC's for each room
and its extremely effective.
Im letting the IRC's to all the work so if theres a demand for heat the IRC sends the IR command to switch the AC unit to Heating and 34 degrees, once the IRC is satisfied that temperature has been reached it sends the OFF command to the AC unit
likewise with cooling, I set the IRC to auto or manual cooling set the room temp to say 18 degress and the IRC sends the IR Command to switch the AC unit to cooling at 16 degreres and again once temperature target has been reached the IRC send the IR Command OFF to the AC unit .
I Have s separate IRC for my radiators in the same room, you could use the two stage function of the IRC but I prefer to keep the AC and Radiators seperate.
You can get specific MODBUS modules for Daikin indoor split units but this will be way over your £1,000.00 budget