I'm building an extension on the back of my house. My neighbour's private drain runs into the manhole on my property, and the local water authority own that manhole and the sewer pipe that goes out the other side of my property. I have obtained a buildover agreement from the water authority, passed building regs and planning permission. Do i need to obtain a buildover agreement from my neghbours for going over their drain (it's private because they are the last house on the run), or is a buildover agreement just something that the water authorities have invented. The water authority say it's nothing to do with them.
The covenants in my neighbours deeds state that they have a right to enter my property for the purpose of repairing or maintaining the drain (amongst other things). I'm seeling over the manhole, putting in a T junction, and connecting that to a newly built manhole further out in my garden, so they won't have direct access anymore from my side to their drain. Do they have any legal recourse there? Do i need to enter into any agreement, or can i just do what i'm planning?