The Consumer Protection Act 1987 applies if you supply in let accommodation "goods" such as electrical equipment upholstered furniture and gas appliances. "Supply" includes hiring or lending goods whether you are acting as a landlord or agent. To ensure that everything in your property is safe, you should get the "goods" checked before you offer the property for rent.
Penalties are severe but, far worse, is the possible harm to tenants.
The Electrical Equipment (Safety) Regulations 1994 state that supplying unsafe electrical goods is an offence. In the event of an unsafe appliance being found in rented accommodation, one of the things Trading Standards would do would be to check that the landlord or agent had taken all reasonable precautions to avoid the supply of that unsafe item. The only way to do that is to have it tested regularly.
A landlord should have a periodic inspection and report carried out at regular intervals. The frequency depends upon the age and use of the property and also may be supplemented by local authority regulations. We would also recommend that the properties are inspected on change of occupancy.