The Government published the more detailed guidance regarding social distancing measures in the workplace on 7 April 2020. This provides greater detail on how social distancing can be maintained where employees cannot work from home. Overall guidance on social distancing in the workplace can be found here https://www.gov.uk/government/publications/guidance-to-employers-and-businesses-about-covid-19/guidance-for-employers-and-businesses-on-coronavirus-covid-19#social-distancing-in-the-workplace---principles
whilst more sector-specific guidance can be found here