Foxes are brilliant at predation, equal only to their lazyness. It is unlikely that they would tackle an adult hedgehog, they weigh between 5-9 kilos and have very sensitive paws and mouths. They are natures bin men and are opportunists; they will eat dead and partially dead wildlife. In urban areas, food supply is plentiful because humans leave their rubbish everywhere. It is unlikely that they would predate hedgehogs.
If you are bringing wildlife into your garden and creating a food source for them, you will be unable to select the species you want to feed. There is always a risk when attracting predators and prey; food is survival in the wild.