Please see links below and if you think you are at high risk and not received a letter use this website, https://www.gov.uk/coronavirus-extremely-vulnerable
Social distancing for vulnerable
https://www.gov.uk/government/publications/covid-19-guidance-on-social-distancing-and-for-vulnerable-people/guidance-on-social-distancing-for-everyone-in-the-uk-and-protecting-older-people-and-vulnerable-adults
Advice for high risk
https://www.nhs.uk/conditions/coronavirus-covid-19/advice-for-people-at-high-risk/