in an assembly, I have created some reference planes (see screen shot)
the problem is when I now make a "new part" I can't reference the planes
is there around this?
No. Once you enter part edit mode (even in an assembly) you only see the planes of the part. However once the part is finished and you are back in assembly mode you can align the part to that plane.
Similarly, I often make a ghost part in the assembly that I use for multiple part's critical reference geometry. Then when things change in the ghost part all other parts update.
I assume that your Reference Planes are something that is Project-wide. The easiest way to deal with such coordination is to define Values using the Global Parameters definitions that can be Loaded into each of the Project's files and applied to construct (& coordinate) the needed Reference Geometry.