Hi Danny,
I had a look at your case, and unfortunately, I'm afraid there's not much we can do to help you. No one at Avast has direct access to the data stored in your Passwords account, and in your particular situation, the combined actions of formatting the PC and resetting your Account password locked yourself out of the Passwords vault.
It's true that Passwords will require some kind of confirmation after you change the password to the Avast Account. Meaning, that you first need to enter the current password and then confirm using the old password. This is a security measure to prevent anyone else from taking over your Passwords account.
I tested it with my account, and the old Account password was accepted. May I ask you if you changed/reset the account password more than once? In this case, I'm afraid it might be the reason why your original password is not accepted. You can try with one of the passwords you set in between.
I really hope you'll be successful in trying this. Please let me know how it went!