I know this isnt entirely helpful but for my understanding...
You have installed a driveway at your home where there never was one before, to gain access to the new driveway a drop curb needs to be installed from the road onto the pavement, the pavement then forms part of the journey onto your new drive....and finally on that pavement there is this Openreach manhole? Which of course you would need to drive over to get to your drive?
Ahh okay, I see what you mean, sorta like going from a single to a double drive way and the extra bit is over the manhole.
I found this post on something similar for further context:
Solved: Applying for a dropped kerb - BT Community
Good luck, you'll have to let us know how you get on. These things are never easy, my friend installed a new drive in some land he had next to his house, of course had to get a drop curb, there were no complications such as manhole covers and so on but it took nearly a year.