I go to settings - your account - account information - https://twitter.com/settings/your_twitter_data/account
This is where I can typically change account name, when logged in using email and password.
(I've just checked using my other account and yeah, that's the place where I can update my username)
But I've created an account via "login with Google" and I feel stuck.
Any ideas how to update the Twitter username when logged in via Google?