I can access & send from my v. old Tiscali email addy, both POP3 & Webmail, & do so regularly (altho' not many emails received on it). Just never been able to change my pwd.

It seems that the first people where affected some time back and it has been building up since, gf's email was accessible for a day after mine.

I have had access to mine for years, always by POP

gf's tiscali email address dates back to dial up, was accessed via pop, as above the day after mine stopped so did hers.
mine is sometimes via webmail, sometimes via pop, both have stopped.

I suggest you contact them and ask them to confirm that it is not going to be withdrawn.

So far I've spent over 3 hours on the phone over two phone calls and it has been esculated to the networks team. I was told a return call would be made between 24 to 48hours after the last call, this is now 6 hours overdue.
Gf's was able to log in to email today even though I've not mentioned her address to them.

Mine was also back in the day of dial up, it is not my main email address, but I do use it for a few things, which can easily be changed if TalkTalk do get rid of old tiscali email addy's. I have my own domain with email, I don't rely on ISP email.

I'm not bothered if they do, I have access to email via my own domain and some old Yahoo and Gmail email addy's I can use if needed.

TalkTalk have refused access to my email address, lots of exqueses, none of which are valid.
Their action was predetermined and all I needed was prior notice to ensure all was sorted, not a happy bunny to say the least

A further update.
Must have woken someone up with my official complaint, they actually got to ringing back.
They have now changed the story once again, they now say the email is still active, but that they are still making changes that when finished will allow me to change the password and access email again. i'm not 100% convinced this is true but have agreed to give them a reasonable time to sort it out before starting official complaint procedure, via ombudsman, not that it's likely to do any good, but pays to keep them on there toes.