There is a lot of info on the net regarding bats;
The Bat Conservation Trust
www.bats.org.uk
Downnload the bat workers manual
www.jncc.gov.uk
English Nature gives info and mitigation info
www.englishnature.org.uk
Do not forget the local bat groups or the online bat websites,they are always ready to help or advise,basically bats are protected, their roosts are protected wether occupied or not so they should not be harassed at their feeding grounds.It is the loss of feeding grounds grazing land and farming techniques reducing the volumes of insects available,which is why I bang on about planting for wildlife no matter how small your garden look for the seed mixes for encouraging Bats ,Moths,Butterflies,Birds etc.