DON'T feed wild birds milk, or bread. The bread has no nutritional value to them and merely fills their stomachs, stopping them taking in other, more nutritious food. Milk can ruin their digestion if ingested for long enough. The best thing for most nestlings/injured fledgelings is, believe it or not, minced up Cat Food. It's close enough to what they receive in the wild to be accepted by their digestive systems.
If this bird has a broken leg then it's quite possibly recoverable, especially if it's a fledgeling, rather than a nestling. The RSPB won't be interested, but there's plenty of animal sanctuaries that will. I'd have a look in your local directories just to see.