In reply to Postmanpat:
Generally speaking, Thule makes some stellar boxes... but with a high premium.
Mont Blanc as rather good, and a lot less dough than the Thule.
Not sure what is available in UK though.
For 180 skis, you'll want the normal lenght. So a tad over 2m. If someone makes a 190 or so box, it should also work... but AFAIK it's either full lenght or a tad over a meter (not really suited for skis).
As for the bars, the rectangle ones will work with pretty much all boxes. Wing and Aero-bars might not (they might require wide bar fastening kits, or the sliding t-nut kind of kit).