Some of the species of bat found in the UK may sometimes roost in loft spaces. They don’t chew or cause any serious damage but their very sticky urine can obviously be messy and large colonies can be noisy. Concerns about diseases are unnecessary as long as you do not handle the bats. As it’s illegal to disturb bat roosts, their presence can put a block on building work.
The problem with lethal control
Bats are amongst the most highly protected of Britain’s wildlife and it is illegal to injure or kill them.
It is actually illegal to handle bats unless to seek treatment for an injury or illness and it’s also illegal to set traps for them or do anything to damage or block access to their roosts so taking any direct action yourself is not legally possible. If you have bats in your loft then The Bat Conservation Trust is a good source of advice. Before taking any action including repair or maintenance work to the area you will need to contact your Statutory Nature Conservation Organisation