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 European Protected Species (EPS) Licence, which may allow you to carry out the work subject to certain conditions. In Wales, the issuing authority is the Welsh Government (links can be found in 'Related Information').
In order to obtain the licence, you will need to gain the services of an Environmental Consultant who will help you to plan what will happen to the bats. Bats are a protected species and the licence will not be granted if there is no proposal included for re-homing the bats.
If work is carried out without consulting the above organisations, 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.