I feel your pain on that one. DDad bought a bungalow opposite me. Between the bungalow and the neighbours was a low, approx four foot chain link fence. While the sale was inbetween exchange and completion the neighbours replaced this fence with a six foot orange number topped with a hideous curved trellis that added another foot and a half to the height.
The bungalow is, like your house, only three foot from the boundary, so DDad’s little bungalow now looks straight out onto fence, and the view of hills and church that was there before is now blocked out. The light too is massively compromised.
It is unclear from the deeds and historic documents which side owns the boundary. The previous owner died, so we can’t ask him, but we know he had an acrimonious relationship with the neighbours. It seems clear that they seized their chance when the property was between owners to do what they wanted. When DDad expressed disappointment and asked if they could come up with a compromise, they told him it was tough and he didn’t have to go ahead with the purchase if he didn’t like it.
It’s such a dick move. Although DDad remains polite to the neighbours, he thinks they are selfish arseholes. He’s really dragging his heels moving in and I think this whole fence thing is partly to blame. As you rightly say, just bloody communicate, and try to find a solution that everyone can live with.