It comes down to area and exposure. As a rule of thumb the 2300W suits a compact, well-sheltered spot such as a porch or a two-seat balcony, the 3400W covers a typical four to six seat dining area under a veranda, and the 4500W is for larger or more exposed terraces. If the space is open on two or more sides, size up rather than down - radiant heat is lost quickly to wind.

It is a fixed appliance and must be hard wired by a qualified electrician to BS 7671. The 2300W and 3400W models will usually run from a suitably protected radial circuit; the 4500W draws more and often warrants its own circuit. Have your electrician confirm the supply before you order.

At least 1800mm above finished floor level, with a minimum of 1000mm to any combustible material such as timber, fabric or planting, and 500mm between adjacent heaters. Those are minimums from the Bromic manual - going higher spreads the heat over a wider area but softens it, so most installations sit between 2100mm and 2400mm.

Yes. It is rated IPX4, which covers splashing and wind-driven rain from any direction, so an open-sided veranda or pergola is well within its design brief. It should not be submerged, jet-washed or installed where water can pool against the housing.

Only the finish. Output, dimensions, mounting options and controls are identical. The white version is popular under painted soffits and rendered walls where a black unit would stand out; black suits dark-stained timber and anthracite aluminium verandas.