It is possible, but it depends on the wheel. Some wheels have a more bulbous back area, which makes it harder to get tehm to fit. If they have quite a bit of balancing weight on them then it'll probably be impossible. But if it's not far off then you'll have to grind the calipers to round off the ends. It has been done before and isn't that hard to do, as there's plenty of metal there to go through. There was an issue of Fast Ford where Jamie did this conversion on his Fiesta with 15" Pro Race 1.2s on, so if you can find that bit, it might be on the website, it'd give you a guide.