Yep the Heat (Warmth would be more accurate term) output is low and almost constant which works a treat in a nicely insulated and air tight box but not in your typical old Manx stone cave specification home You need shear quantity of raw heat in a typical older building . Mine uses undefloor piping which is about the best system to use alongside an air or ground source but as for cooling the problem then is condensation on the pipework I find, especially at low water temps like 6c so you're limited to around 18c to avoid this which is kind of useless at cooling effectively but still make your elecy meter stack up the Units nicely for Manx Utilites. Clever valves and what not can deal with the hot water/cold water issue but I gave up trying to cool my place with it more because its far cheaper to just throw all the windows open and allow the cool evening air to drop the temperature enough to sleep comfortably but I'm off work so that works fine going to bed around 10pm - 12am! Wouldn't be much use earlier in the evening though.
Very tempted to buy an air con with the internal wall mounted fan coil unit just for serving the bedroom in mid summer, cheap as chips too .