You can contact your local pharmacy to order baby formula, allowing a couple of days for this to be delivered. You'll normally be required to pay for this in advance.
Each formula company have updated their websites to provide COVID-19 information, and local supermarkets sell a variety of formula brands; please see the supermarket websites for more details. If your usual brand isn’t available, you can find information about what's in each formula milk on the First Steps Nutrition Trust website.
Unicef have also provided guidance around best practice for infant feeding during the COVID-19 pandemic.