Those racks are on the new ones, and cost £500 as an extra and are apparently rubbish.
TBH, i hate saying this, but on a 1.2 corsa, you’re best getting a rear mounted rack. A roof rack will act as a parachute, and it’ll take ages to get going when accelerating. It will, however, be more secure.
Something like a Saris Bones would be fine. Just check the straps every say, hour of driving that they haven’t come loose. The amount of times i’ve seen bike racks fully loaded hanging off the car (with straps loose or just dangling) is shocking.