the place where I was parked has no signs whatsoever defining the restricted period. In addition, the line is so faded to the point of being invisible.
As regards the line, I don't think you'd convince an adjudicator on this one - the photos show a yellow line.
So the only remaining issue is whether it's within a CPZ or signed independently.
There isn't a stand-alone traffic sign to be seen, which probably indicates that it's within a CPZ.