Gov.uk has release updated information regarding clinically extremely vulnerable persons please see the link below for more information, including who is classed in this group, what has changed and what to do if there is a local lockdown.

https://www.gov.uk/government/publications/guidance-on-shielding-and-protecting-extremely-vulnerable-persons-from-covid-19/guidance-on-shielding-and-protecting-extremely-vulnerable-persons-from-covid-19