List of reputable heat pump suppliers and fitters

there is a gentleman in northern ireland doing my job. This boy knows his stuff. He uses a heat pump from america which is seen as superior even to the german machines.Interestingly, he suggests 1 stat per floor. Probably 3 at most in a house. He uses clever devices called Datatherm which is developed in England. All this sounds quite expensive. Its not. I am paying middle of the road money (not cheapest and definetly not most exp) and I am getting an excellent system and importantly, put in by a man who knows his stuff.