Changing our outdoor PIR lantern and the developers as usual didn't leave very much length to the wiring. I've got just enough to bring it inside the light housing which I've terminated for now into a terminal block strip. This is 3 core and earth cable but is there a way to know whether it's 1.0mm or 1.5mm cores? The house is about 10 years old, would it be common for it to be one type over the other?