Material parameter collections work a treat and also make things a whole lot more efficient when changing a parameter on a lot of actors using the same material, in comparison to setting up a dynamic material and applying it to each individual actor.
If any one else has this issue, I found these references really useful:
https://docs.unrealengine.com/latest/INT/Engine/Rendering/Materials/ParameterCollections/index.html
https://wiki.unrealengine.com/Location_Based_Opacity_in_UE4_-_Part_2