I'd use the same approach as wrangler_rover except I'd start by looking at the website for The Roofbox Company because they supply kit from other manufacturers as well as Thule.

There is a hire company in the area requested by Benet: www.welwyn-roofbox.co.uk/

Their price list, however, suggests to me that eBay is likely to be the cheapest option.

A pair of £95 car-specific roof bars for a "rail-less" car cost me just £21 on eBay.

Edited by John Boy on 22/03/2017 at 20:08

This worked reasonably well on a long trip over Easter. But you have to get the attachment point between the bar and the bracket at exactly the right position, or else the angle on the bracket is wrong and the bolt will unscsrew itself as the wind goes past. I realised this when the car was parked all day in a windy part of Northumberland and by the evening that bolt had *still* loosened to finger tight!

It's not really a nut that is screws into, more a kind of curved saddle. I don't think it's nylock. Just about OK when the angle where the bracket meets the edge of the roof/top of the door is right, but that angle has to be 'bang on'.