I've been trying to find the Thule 1581 fitting kit for weeks now. But nobody has one....anywhere. So I carry my bike in the boot with both wheels off. If you're worried about mud getting in your car, get one of these
I got one and was really suprised by how much pressure it can hold. Only uses about a litre of water to hose down the bike.
My better half also has the megane 3 coupe so the roofrack is no option for me, otherwise she'd be getting a roofrack for xmas