With workplaces being less occupied and stagnant water posing an increased risk of Legionella related illness, The HSE have provided advice.
https://www.hse.gov.uk/coronavirus/legionella-risks-during-coronavirus-outbreak.htm
If you are an employers or a landlord then you have a duty to protect people by identifying and controlling risks associated with legionella. The easiest and by far the most recommended way is to choose a professional organisation to provide you with a risk assessment and supporting services. A great place to start looking for a provider is the Legionella Control Association directory.