Following the Government announcement in relation to obtaining confirmation of your COVID vaccination, please use the link below for the gov.uk website which details all of the necessary information to help you.
https://www.gov.uk/guidance/demonstrating-your-covid-19-vaccination-status-when-travelling-abroad
It is important that you download the NHS app.
If you do not have a smartphone, please contact 119 as they will be able to assist issuing a letter.
As per the Government website:
Do not contact your GP surgery about your COVID-19 vaccination status. GPs cannot provide letters showing your COVID-19 vaccination status.