Ford do spacers. They're 12.5mm too, slot of the fiesta st guys fit them (including me). Not too sure if they'll fit a mk5, but have a look on the zsoc forums and see if they suggest anything.
Lowering 40mm over 12.5's on a mk5 I would think would possibly rub. Personally I'd just lower and get Escos wheels. Mk5 zs's look ace on those!