All bat species (and their roosts) are a European protected species. There are strict regulations with regards to bat conservation that you need to be aware of prior to starting any project of this nature. In England, Natural England can grant what is known as a Bat Mitigation Licence, which may allow you to carry out the work subject to certain conditions.
In order to obtain a Bat Mitigation Licence, you will need to gain the services of an Ecologist who will help you with your mitigation licence application.
In Wales, you must apply for a protected species licence from Natural Resources Wales (links can be found in 'Related Information').
If work is carried out without obtaining a licence, you may commit a criminal offence and could be liable for a large fine or a custodial sentence.
For more detailed advice on this subject please contact the Bat Conservation Trust, linked in 'Related Information'.