Public Health England has approved an antibody test made by Roche, which might now be used to help determine how many people in UK has been infected with coronavirus. https://www.bbc.co.uk/news/health-52656808

This is not the same as the 3.5 million finger prick blood tests bought by the government which proved to be unreliable. This requires a blood test so would need to be done by a health professional and then sent to a lab

What is still unclear is how much protection the presence of antibodies will give to coronavirus or how long any immunity may last.