I have tried several roof bars/racks on my LWB Mav, since I don't have the factory roof bars, most of them do not grip the recommended points ( edge of roof, very well, and a quick twist and the rears come undone.
If yours had been a SWB then where do the fixings go.
Be sure it will fit your car first. I have not tried the Paddy Hopkirk ones so can't comment on them.
Any roof rack/cross bars create a horrible humming noise and will increase fuel consumption. So take them off when not required, you can't keep this in the boot just in case you might need them while you are out.
Just my thoughts.
Regards,
Rustic