I'll _respectfully_ suggest that you don't know what
you're talking about. The 'front elevation' essentially can't
be changed without 'planning permission' - but - other things
being equal PD will permit one to add a large volume
to the rear of a house - that's _not_ "limited to the front elevation "
I would recommend that you familiarise with the legislation ...
many D_I_Y manuals have helpful isometrics of what's
permitted and not.
Unless you're not intending to mean what you've written.

You can add a porch to the front of a house without planning permission
usually,
if it's within a certain size, 3m2 foor area if I recall correctly.
Simon.