Try entering the following:
FTP server address: w w w.yourwebspacename.talktalk.net (without the spaces between the w's)
username: [email protected]
Password: your password
Don't use http at all.
Bear in mind that if you upload a FrontPage web to a server via a third-party FTP site you'll lose the functionality of the special FP components if FP server extensions are running.
Some ISPs prevent access to their FTP servers via any other ISP connection - this is done to prevent warez dumps. That means that if you try to access one ISP's FTP server when connected to the internet via another ISP you will be denied access. Not all SPs do this, and I don't know if Talktalk do - my guess would be that they don't, but it's worth checking.
If you're stuck, email me with your login details, and I'll take a look at the server for you.