An air-to-air heat pump can cool and heat your room but doesn't provide hot water. 

Therefore, you need an alternative unit to heat water for your showers, baths, and faucets. 

Choosing the right type of heating depends on how much hot water you need for your home and house space or budget.

 

You may consider an electric immersion heater, shower, or a "point-of-use" heater. Point-of-use" heaters can heat water with gas, liquefied petroleum gas, or electricity. Gas heaters require a chimney, while you can install your heaters in an inconspicuous spot under the sink.

Whether an air-to-air heat pump will save you money on your energy bills depends on the design and operation of the heat pump and the system you are replacing.

 

Saving money is not everyone's primary motivation for installing a new heating system, but you need to ensure that installing the system is affordable.

You had better ask your installer for a quote on the heat pump operating costs.

The fan coils/blowers are connected to the external unit via ducting.
They are typically installed inside the exterior wall near the outside unit to reduce the interior required duct length.
When planning a multi-fan system, installers often try to minimize the length of ducting to each fan location.
You can ask the installer about possible ducting routes before they begin work.