Legal

Prevention of Damage by Pests Act 1949

If in the case of any land it appears to the local authority . . . that steps should be taken for the destruction of rats or mice on the land or otherwise for keeping the land free from rats and mice, they may serve on the owner or occupier of the land a notice requiring him to take, within such reasonable period as may be specified in the notice, such reasonable steps for the purpose aforesaid as may be so specified; and where the owner of any land is not also the occupier thereof separate notices may be served under this section on the owner and on the occupier.

The Health And Safety At Work Act 1974

Employers must take necessary measures to secure the health, safety and welfare of employees and the public in general, to avoid, for example pathogenic disease carried by pests, slippery conditions caused by bird droppings, bites from fleas and contamination of food caused by droppings.
 Penalties include improvement notices, prohibition notices and maximum penalty of two years imprisonment plus unlimited fines.

The Food Safety Act 1990

Any businesses that grow, store, distribute or sell food must ensure the food is safe to eat.
It is an offence to treat, sell, advertise or be in the possession of food that is unfit for human consumption.
Businesses must prevent food and food products being damaged or contaminated by pests. Food premisses must be kept in good condition, clean and free from rubbish which may attract pests. Penalties for non compliance include improvement notices, prohibition orders to close premises, seizure of unfit goods. Local courts may decide on disqualification from catering fo up to two years, fines of up to two thousand pounds and a six month prison sentence per offence or, if a “key” offence, fines may rise to twenty thousand pounds. Crown Courts can impose unlimited fines.
The subsequent Food Safety (General Food Hygiene) Regulation 1995 contains more specific and detailed information relating individual areas of the food industry.