The message ilgate.org
from "Grumpy owd man" contains these words:

Should they have had planning permission to build so close?
Is it a job for the Council or BCO or do I have to live with it?

Planning permission isn't always necessary. However, the rule I had to
obey[1] to get PP for the conservatory I'm (allegedly) building was that
from the centre of their window a line out at 45° must not intersect
with my construction.
I deliberately didn't put windows in the side because I didn't want to
overlook the neighbour's patios.

You could of course put up a fence that stops 'em opening their windows
- but it's better to solve these problems amicably. Which is why I
talked to the neighbours before even applying for permission so I didn't
upset them.

[1] Had to cut a corner out to comply. Stupid thing is that John next
door said he didn't care because all he'd have seen would be a little
bit sticking up over the fence. Damned silly.

--
Skipweasel
Pay no attention to that man behind the curtain.