Why does perlin noise fill only the shape of the first uv island

Hi,

Why does the perlin noise texture fill only the shape of the first uv island when dropped in? When I move or scale the noise, this seems to only affect the original UV island shape from when it was first imported. It's as though it has a mask already on it. I can't see any other layers or masks affecting this. I have just drag and dropped to the model and selected height. Maybe there's a workaround or something to get this dealt with on my project.

Any advice much appreciated!