Bought a Thule motion XT XL earlier this yr with the aero bars, it's a large long box but fits nicely on top of my Disco. I bought it through Halfords and they fitted bars and box on site.
Roofbox.co.uk is where I bought mine and they have been recommended by PHers many times since. I bought an Atera box, has stood being used and abused really well. I think Thule and Atera are both quality brands.
