Hedgehog numbers in the UK are plummeting. There were 2 million in the mid 90s, now there are less than 1 million. The good news is that it is easy to do something about it. Unless, that is, you live in central London where there are none left!
Hibernation: Nov to April depending on temperature
Breading season: Typically May. Babies born and remain in the nest June/July
Summer shelter: July to Sep in poor weather and to avoid predators.
Hedgehogs are carnivores and eat practically anything. Cat food is good as is a bowl of fresh water. Do not feed them an cows milk.