Getting a sunroom in need advice

[als30]

Come July getting a sunroom done I'm in a mid terraced house with neighbours either side
Had the architect out today taking photos and mesurments but said something about drainage and would need access to dig up neighbours garden to get to it is this right and what happens if the guy says no

Can't answer these questions, but I think you should speak to your neighbours and explain you want to have some work done and it might mean having to do something on their land and see what t heir response is? Are you aware of any rights you might have over their land in terms of drainage or anything like that?