Ground-mount needs a garden and a planning conversation. Roof-mount is the UK default. The choice usually settles on garden size and roof orientation.
Roof-mount fits the standard UK install case — no garden disturbance, permitted development covers it, fitted price runs £1,650–£1,900 per kWp. Ground-mount runs £1,750–£2,150 per kWp, needs garden space, usually needs planning permission above 9 m², but can hit perfect tilt and orientation. Best fit: rural homes with bad roof aspect.