If you’d like to apply for a passport using a paper form, you will need two identical printed photos. Your printed photos must be 45mm high by 35mm wide which is the standard size used in UK ...
Women with darker skin are more than twice as likely to be told their photos fail UK passport rules when they submit them online than lighter-skinned men, according to a BBC investigation.
You can check entry requirements for individual countries on the UK government's website. You can renew online at HM Passport Office or by filling in a paper application from certain Post Offices.