Thanks stevedrummond, Sorry for slow reply its taken a bit to get this working..
I haven't doe this exactly as your example, but without your answer I would still be none the wiser.
I am now using the filter as per your suggestion. But rather than have a Hidden Field on the XaaS with the results to filter... I have the Action hitting the API and pulling it back and then I am filtering it.
I was struggling to get the filter to work, but after importing your package and seeing how you did it, I was away.
Though I still dont see why the drop downs on XaaS are not the same as IaaS, in being searchable.
Thanks Heaps!
Jono