I was not thinking of running heating and cooling at the same time. Simply that if you run a heat pump in reverse, you can use it for cooling. So you should be

I was not thinking of running heating and cooling at the same time. Simply that if you run a heat pump in reverse, you can use it for cooling. So you should be able to use the same device for heating in winder and cooling in summer. Even portable aircon's do this. The tricky part here is that you want heating to transfer heat to water, because radiators are much nicer than heated air. These Co2 based heat pumps are good because they can heat to a higher temperature which is necessary if you want to use your existing radiators or your house is difficult to insulate. But I'm not sure it would work well to use 'radiators' for cooling. Apart from any other reason, you won't want to risk freezing them.