If you can live with the design of the wall units hanging in your historic townhouse, that might be a solution. It could be cheaper, but you will be altering your rooms with those units. I would go high velocity with linear diffusers in the walls or pin-point diffusers in the ceiling, driving the conduits within the walls. More expensive, more attractive, and better resale value. Not to mention that you will have to put several condensing units outside, which will also interfere with your front garden and back yard.