Solar PV systems only need daylight, so can work in most locations. However, the output changes based upon the amount of daylight available. They will always be most efficient when placed in unshaded areas, facing at least partly South-facing. Any direction in the southerly arc between East and West will work at no less than 85% efficiency though. Output depends wholly on the strength of the sunlight, not on the outside air temperature.
No planning permission is needed for most home solar electricity systems, as long as they’re below a certain size. You should check though if your home is a listed building, in a conservation area or World Heritage site.
The inverter is usually mounted on a wall inside your property, near the solar panels, or the household consumer unit. It will usually include a meter to show how the system is performing.