If you know where bats roost let your local bat group or The Bat Trust
www.bats.org.uk know,especially if it is a house or building (lots of bats use old trees). Many bat colonys are lost because nobody knows they are there and cannot advise about them or defend them (using the law) when building work or development occurs.
Builders and developers are "usually co-operative" nowdays,but English Nature
www.englishnature.org.uk,would like to know of any extension or roofing work on private houses where bats are known to roost or developers move in to convert barns or older buildings,most Local Authorities and Local Police Stations have a Wildlife Liason Officer who will assist or advise you.
Strangely it is the NIMBY attitude of people that saves most of these beautiful endangered mammals,when an approach is made to the owner or developer they can actually become proud to acommadate the bats!
Remember you may be the only one that knows about a site, tell someone and help them survive.
Bats are protected by law it is illegal to intentionally or deliberately kill or injure capture or take them
delberatelydisturb bats(whether in a roost or not)
recklessly disturb roosting bats or obstruct access to their roosts
damage or destroy bat roosts
posses or transport a bat or any part of a bat unless aquired legally sell or offer for sale or exchange bats or parts of bats
the roost is protected whether the bats are there or not!!