OK - I have just had a look at Talk Talks support pages. There are some things I don't fully understand - one is that when using talk talks software and modem/router, it implies that there is a two stage connection process - a connection to talk talk ISP and THEN a login using phonenumber@talktalk and a password - but it isn't clear if that is also the initial password. I don't think the Draytek router is at fault, but it may be that you are not getting all the information from talk talk. In particular I am wary of statements that say that talk talk won't allow you to connect without their software on your computer - implying some other security system that may only work with their hardware.
I don't think I can help any further - anyone else here who has had experience of connecting a draytek router to talk talk may be able to help, so it may be worth starting a new thread. (Something like "Problems connecting a Draytek router to Talk Talk ISP) and state what you have done (you might want to cross reference to this thread) It might also be worth posting a similar thread on the Draytek forums as it is no longer an upgrade issue.
Otherwise I tthink the best sources of help are (in this order) Talk Talk's help desk and then the Draytek support line - but I don't think it is a Draytek issue.
If that doesn't resolve it, then either use Talk talk supplied hardware (I see they sell a wireless router) or change to another ISP.
I'm sorry this hasn't worked out for you - but this is definitely an authentication issue and one that I think only talk talk can offer authorative advice.