Actually, both would be the "front elevation" as it were. It's any side
facing a road (and usually public footpaths).

My opinion is that by developing the "open space" on the corner plot
results in the entrance to the road being narrowed and will affect
the values of all the properties in that road.
Is that grounds for complaint ?

Don't even mention house values. Keep your mouth shut on that, or they'll
put your complaint in the bin. Road safety is one possible. Changing the
character of the area is another. You'll have more luck on the that ground
in a nice Victorian villa area than a 1960s council estate.

One possible that works in some areas is affect on parking. Some councils
publish a minimum number of off road parking spaces for certain sizes of
houses. With the house getting smaller, possibly using space originally used
for off road parking, a restriction could be invoked.

Christian.