Hopefully this will help others in a similar situation.
Having recently signed up for business broadband with Vodafone to act as a failover service in case Virgin went down, I came to set it up on my Draytek Vigor 2860n.
I called the Vodafone helpline to get the username and password. To ensure there was no mistakes they emailed it to me, [Username]@businessbroadband.co.uk & the corresponding password, however this user is INCORRECT.
I kept getting the issue in the Draytek interface "Error: Username or password incorrect". I called Vodafone several times and each time they recited the same username and password.
It turns out that the actual username for it should be [Username]@businessbroadband.vodafone.co.uk
As soon as I changed it over to that *bingo* off it went
