Can an air source heat pump work alongside a boiler?

Yes. This is known as a hybrid system and is becoming more and more popular. Essentially, the property would predominantly use the air source heat pump for heating and hot water and when commissioning the system, you would set up the controller so that the boiler would provide supplementary heating and hot water in certain conditions, such as:

• If the temperature outside drops too low
• If the air source heat pump cannot reach temperature within a time limit
• If the cylinder needs to carry out a legionella cycle
• If the air source heat pump fails