I depends if it's going to be a regular thing or not. If not then a £30 lidle job will probably do. If You want something a bit more substantial look at the Saris Bones, an alternative is the Mont Blanc range. Good quality and cheaper than Thule. If your bike is worth the annual wage of a family from Dundee, get a tow ball. Bike roof racks are bad! The wind/rain eats headset and it kills fuel efficiency. Plus it can be a pain to load/unload your bike(s).
Cheers Scott I will look the carriers that you have mentioned, I am just a bit wary about using a boot carrier on the fiesta bumper.