From 1st April 2022 there is no need for the public to routinely test for covid using lateral flow devices (LFT). However, should a GP require you to get a test the following guidance had been given by NHS England:
All NHS patients in a community or primary care setting requiring a test by a clinician to support clinical decisions during their care and treatment pathway should be offered a lateral flow device (LFD) test as part of their usual diagnostic pathway. Patients should be directed to the gov.uk website to order their tests, where they will be asked to confirm that their clinician has requested this. This is a change in testing technology for this group of patients.
You will need an email address to order the postal LFT kits. The website is www.gov.uk/order-coronavirus-rapid-lateral-flow-tests