Hi Brian I have only installed and worked on air/air systems (I believe in sticking to what you know) but common sense says geo would give you a more constant heat gain, it would also be much more expensive to install and I guess (and it is a guess) the system would be a one off, designed for your property no doubt a good system but who would carry out any repairs and how soon could they get to you if in the middle of winter if you have a problem? As a ball park figure you will need 25/30kW output from the system Hi Sallyb the £50 coolers use water as the cooling medium which means you will be putting water into the air in the room you are trying to cool which in turn will give you a very humid room. The £200 mobile unit will need to be vented to the outside (you cannot destroy heat only move it from place to place) is liable to be noisy as the compressor and both fans will be inside the room a fixed split system has the compressor and one fan outside the indoor unit has the cooling block (evaporator) and a tangential fan (very quiet) you pays your money and makes your choice Hope this helps Stephen