My neighbour has a lawful development certificate to perform a hip-gable loft conversion on their detached house. They do not have a side-return on the side of their house next to ours, with their external wall being the boundary. Their existing eaves overhang our side return (as do our eaves) and as such there is a very small gap between the properties. Their plans show these eaves will be removed to form one of the gable ends. Would they be able to do this work without access to our side return or above air space?