It may be that information about me stored by my email ISP provider was lost when it was taken over, and all there is left linking my account to anything is a password. If that password has been compromised, then who is to say an imposter would not use this to change the password, putting the whole account out of reach of the true owner? There needs to be some verification process therefore to link the account with its true owner, who once properly identified can change the password. Possibly one way to do this is to link it to a third party email address that does have verifiable contact information, and from there cover both TalkTalk and any owner, since any malicious hijacking of an account could be traced and dealt with. I welcome other ideas.
Just noticed this post - the answer depends on who your original ISP was ... for me - it was Nildram (gotadsl.co.uk) - which was taken over by TT Business - so I stilll have access via TTB's website - if yours was AOL - You still have access to your old account on-line