Then surely it's the local authorities responsibility to make it safe before you do any work on it? Seriously mate, a friend of mine is a fearless brick-shithouse sized roofer, and they discover nests in roofs all the time at this time of year. They down tools immediately and wait for...
Indeed. Also, if the nest is a danger to the general public, the Council will remove it for you. This obviously depends where the nest is located though. Have fun!
Don't work anywhere near it at the mo if I were you. They're pretty aggressive at this time of year. I'd get someone specialized to move it/make it safe first, or you may have a rather painful afternoon!