These solutions are essential for vehicles that cannot have roof bars, or where roof mounted items present problems. Such as electric cars where the range would be reduced, or for those of us which are vertically challenged making roof access tricky.
Thule 300 Litre storage box, mounts onto the Velospace cycle carrier which costs from £569 for the 2-bike version (view Velospace here).
The advantage of this over the Arcos is threefold: 1. The rack/box has a foot-operated tilt mechanism so you can access the boot. 2. It is collapsible making it easier to store. 3. It's a 3-4 bike rack when you don't need the box (1 bike possible with the box). The main downside is it's only 300 litres whereas the Arcos Large is 400 litres.
The Thule Outset is a 2-3 person tow bar mounted tent. Like a roof-mounted tent, but more aerodynamic so better for fuel-economy and it won't reduce the range of an electric car to the extent a roof-mounted one would.
Sits on a frame 21" off-the-ground to avoid mud and wildlife, easy to deploy and stow away. Features too many to list but include integrated mattress, fly-sheets and storage pockets. Once setup it can be detached from the tow bar so you can use your car for day trips.
Thule Arcos - towbar mounted storage/cargo box. Hard-shell lockable box with integrated lights (13-PIN plug).
Prices include the base platform that the box mounts onto.