The message
from "KD" contains these words:

Hi all,
Just to let you know that I received a reply from the NHBC stating that
if waterlogging was present within a 3 metre boundary from the house then
the builder was obliged to put this right - otherwise tough luck.

That's only one measure of constraint upon the developer/builder.
Scottish planning and building control standards are equally binding;
it's worth asking those local departments for their opinion and support.

Janet