What are our options? (Diagrams included!)

[OutsideToilet]

We are looking to extend our property at the back. Neighbour B already did the same extension year back and we are looking to bring ours in line with theirs, give up shared access as they did so we can have a private yard area at the back of our house and then we will use part of our garden (it doesn't show the length of our garden on the diagram) to add a drive up there.

The problem is we have some unused outside toilets which mean when we knock down our outhouse part of it will be sticking into our yard.

There are two toilets inside one belonging to my neighbour A and one to us. I've lived here 8 years and have never had access to it, he blocks the entrance to his outhouse and this part of it feels very much "his" depsite one of the toilets being ours.

We'd ideally like to knock straight down through the outside but it cuts through the toilets. He doesn't use his toilet area at all which makes it even more annoying that it'll be sticking into our yard.

Do we have no choice but to have this sticking into our yard?
If we have to have it we are thinking of saying we are going to brick up the entrance to our outside toilet at his side and then putting a door through on our side to get in and then at least we can access it. We could maybe turn it into a nice outdoor toilet for when we have parties so people don't have to walk through our house.

Does anyone know what the rules are when a neighbour says they don't want you to build an extension? He isn't the friendliest of neighbours

I hope you enoy my diagrams

Your diagrams look very professional . But I can’t read them and when I zoom in they go all blurred. From your writing I think having an outside toilet for during parties would be a great idea.

I've managed to crop them if it makes a difference, wasn't blurry when I looked!

Bump for people to appreciate my excellent diagrams

I love your diagrams!
Have you checked your deeds as if where you are planning to extend is shared access you may not be able to do so, or at the least I think you would need your neighbours permission?
Was Neighbour B shared access as well?
If you can extend then I like the plan you have made in the second drawing but I don't think you can assume that you take space from the neighbour A toilet so I think you would have to have that jutting into your new yard and reconfigure your toilet so that it's accessed from your new yard and brick up the access from his outhouse.

From what I understand you kind of "give up" your shared access (neighbour B did this) so the part of shared access infront of neighbour A will end up being just his and I'll no longer drive over that part. the back part of shared access remains shared because me and neighbour B have to drive over it.

I'm quite liking the idea of having an outside toilet, we can use it to store summer garden furniture too if we get something that folds up!

Your diagram is suggesting you would be wanting to use the land/ex area that belongs to neighbour A plus use their outhouse to gain access to your WC?

Why would they agree to this?
Unless you are going to exchange something with them or give them money for their land?

@thisisthebestest I'm not sure what you mean by that sorry! Our plan is to essentially fence off around the land that is ours and then put a door from our side of the outhouse into our toilet which is for some reason in his side of the outhouse. So we wouldn't need to go through his land at all anymore with this plan! I realise now I didn't update where the new door would go on the diagram

Aww ok.
Have you looked up 'permitted development' - I think if your plans fall within that neighbours can't object?