https://www.gov.uk/guidance/coronavirus-covid-19-advice-for-uk-visa-applicants-and-temporary-uk-residents#inside-UK
If you’re in the UK and your leave expires between 24 January 2020 and 31 May 2020
Your visa will be extended to 31 May 2020 if you cannot leave the UK because of travel restrictions or self-isolation related to coronavirus (COVID-19).
You must contact the Coronavirus Immigration Team (CIT) to update your records if your visa is expiring.
You should provide:
• your full name (include any middle names)
• date of birth (dd/mm/yyyy)
• nationality
• your previous visa reference number
• why you can’t go back to your home country, for example if the border has closed
• date of birth (dd/mm/yyyy)
• nationality
• your previous visa reference number
• why you can’t go back to your home country, for example if the border has closed
We’ll let you know when your request is received and when your visa has been extended.