shared downpipe landlord

Hi all, My dad lives in a semi-detached house with the shared down pipe being on his neighbours property. The neighbours did a loft extension and remodelling of their house and during this time they have drilled into my dads property and moved the down pipe to his side without asking...

We have a 1901 terraced house with neighbours on both sides which have been converted to HMOs. The gutters from one of the houses drain into a shared down pipe and to the drain on our side. About ten years ago the house to the left was converted to become shared housing and a new kitchen was...