Mark1919, good evening.
OK not every crack in a building is an indication of Subsidence.
Internally. if the cracks in the Artex are [reasonably] straight then that could?? indicate that the cracks have formed and are following the plasterboard panel, Question? are these cracks on the ceilings???
As for the external crack, or are there several cracks?? it is simply not possible to pass on any meaningful comments, because there are no references in the images posted to give an idea of where these [or this] crack is located.
Having said that, [deep breath] the crack in the image appears to be thermal in origin, is that external crack [roughly] in the center of a wall? or is it somewhere else?
Sorry no definitive reply, but at least something.
Ken