On Sun, 23 Jul 2017 15:39:31 +0100, Bert Coules wrote:

I live in a semi-detached bungalow. My neighbour has complained that
the dormer window of my new loft conversion overhangs the boundary
between our properties because it hasn't been built in exact accordance
with the plans.

If the window overhangs the boundary presumably you have also encroached
upon your neighbour's loft space?

I think he is just out to cause a nuisance.