TL;DR:
Yes, you can install solar panels on a flat roof. Modern ballasted mounting systems are non-penetrative, so there is no drilling through your roof membrane. Panels are tilted at around 10 degrees and can face south or be mounted east/west depending on your roof shape. No planning permission is needed for most properties. A south-facing system in southern England generates around 900 kWh per kWp per year. Costs start at roughly £1,200 to £1,800 per kWp for domestic systems.
