For security reasons, if you try to sign in to your account more than three consecutive times using the wrong details, you'll be automatically locked out.
After 20 minutes, you'll be able to try again. Please make sure you check your details carefully.
If you've forgotten your password or username, click Forgotten your password? or Forgotten your username? on the My account sign-in screen.
Handy tip: if you're having difficulty remembering your username, why not make it easier to remember by using your email address as your username?