You will have 2 teams of engineers booked in the first one will do the pull of cable from the cabinet to the house before the install date / time, then the 2nd engineer will install the external box and all the internal boxes / connections.
The first team will be 2 people to do the pull of cable, I would not advise disconnecting your previous BB as if the first team come across a blocked duct then it may be delayed.
I'm a Very Insightful Person, I'm here to share knowledge, I don't work for Virgin Media. Learn more
Have I helped? Click Mark as Helpful Answer or use Kudos to say thanks