Bike racks / carriers

[Captain Peanut]

Off to Devon again this summer and the OH has decided it would be nice to take the bikes with us.

We've had a look around and it appears that you can hire the roof rack type carriers for a reasonable price but I wondered if anyone else has done this with their ZS and if there are any pitfalls (aside from massive drop in MPG)?

My biggest worry was about the weight bearing ability of the cars roof given that it would be carrying 3 bikes.

Cheers

Olly