I have found the answer to my question below but didn't delete incase its useful to others:
Thanks Johnbaker , I tried that and got to export MPEG4 UHD 3840x2160 @ 25 fps
My PC answers all the requirements of processing power with 16GB of RAM as well as a good graphic card
However whenever the export completes all I get is a black blank video!
I have the upgrade Movie Edit Pro Premium 2016
AH OK FOUND IT ITS MY FAULT forgot to have the Calculate video effects on GPU option on the export dialog checked (as Johnbaker advised "ebros" on this forum...made all the difference