US and UK passport photos are different, but there a number of ways to get photos that meet US passport photo requirements that are published on the embassy website. 1
The embassy has lists of photographers, however most professional photography studios have camera settings that meet the requirements. US passport photo requirements are also the same as the photos for US visa applications. Some photo booths also support US visa photos, such as those found outside stores such as Sainsbury's or at railway stations.
If you're tech savvy, you can take your own photos at home following the embassy guidelines and print them yourself, or, send them to a photo printer like Snapfish.co.uk (affiliate link). The US State Department also offers a photo template to help composing your photo. 2