"But what I find odd is, to get highways sign off, they have to do a site visit and provide a cert. Without this you do not officially have an extended driveway."
I think that having a dropped kerb also gives you access rights and some legal protection against other people blocking your access?
Maybe this certificate is what determines if you qualify for these protections or not?
Sorry, this is what I meant, I find it odd that there are many that have done the drop kerb without providing evidence that the man hole was dropped in height and was done by OpenReach. Yes, the cert mean that highways recognise this is a legal entry to your property and cannot be blocked.
If you have a BT box in any part of the area you want to drop kerb, I would think twice about asking BT.
First, they will charge you about £1000 to come out and take some pics, then if you want to proceed, they will charge you around £3000 to make the flu shorter.