The portal Redstation customers should use to manage hosting is located at https://billing.hostinguk.net
You should log in with the email address associated with your account and your password.
There is a password reset function on that page, just click the button PASSWORD RESET and enter your email address to have a password link sent to you.
If you don't remember the original email address you had with your old Redstation account let us know and we can advise further.