To link your Thinkmoney bank account to Plum you need:
This is your Online Banking username required to login to your Online Account Management in the first step. It is 6-13 characters long.
2. E-mail address
The email address you used to register to your Online Account Management.
This is your unique number created during registration to Online Account Management. It is 5 numbers long.
It is between 8 and 20 characters and contains at least one uppercase letter,one number and one lowercase letter.
If you have forgotten any of these details you can find instructions here.