I sympathize. I live in a similar situation.
My immediate next door neighbour is an obsessive gardener whose first act on moving in was to destroy a pretty, well-established garden by removing every single plant, tree and lawn and replace them with succulents and gravel, very noisy. Her choice, but she also removed the borders and her surrounding neighbours' privacy. I planted a shrub border and she informed me she was entitled to remove every leaf and twig once it touched the top of her low fence, and does so, continually.
The neighbours on the other side put up taller fencing, but took exception the the numerous bird tables and feeders she has so retaliate every time birds settle to feed by using a loud klaxon type hooter to scare them off and prevent them soiling their shed and patio. Consequently, they fly over my garden, shed and patio, depositing as they go, and their is no peace in the gardens in summer.
She is also agitating to get a beautiful oak tree outside the bottom of our gardens, and the responsibility of the local council, taken down, and trying to prevent a disused building being used by the Scouts.
Should this happen, they will immediately build on the small area of land, another threat to privacy.