I have decided on a final scale of a 200mm diameter after research into other wall lights on the high-end lighting market. Below is the extra bit of grasshopper definition that I wrote to enable me to scale the pieces. Due to the complexity of the forms it was hard to measure the forms diameter accurately. What I have done instead is created a bounding box which contains the geometry. I then measures the width of this box thus giving me the diameter at the widest point in the form. I then took the data for this and plugged it into a panel which displays the value of this number. I could then increase of decrease the scaling effect watching until this number changed to 200.
Below are the scaled forms-