thanks for your help on this appreciated,
with regard to your question:
"It depends, should all vNics be migrated to the same Portgroup?
Or should each vNic go to the Portgroup (with the same name) on the destination vDS>?"
its not all the same port groups no, they are all being migarted to the same vds but port groups will differ dpeending on the vm...
some vm's have 1 nic, some have 6...
so for e.g. one vm will have 2 network adapters ...
nic1 = portgroup 775
nic2 = portgroup 885
which im hoping i can specify somewhere like a csv and then script a move so it migrates each vm and sets the port group on each nic correctly