Ok thanks both. The issue I had was that, after changing the port to trunk I would lose connectivity. Also if I changed the VLAN tag before then I would lose connection too. Eventually what I had to do was remove one of the NIC's from the vSwitch and create a new vSwitch, add that NIC there after it was configured as a trunk port. Create a management vmkernel port and give it an IP. THen I connected directly and removed the original vswitch and changed the IP onf the new Management port to be the same as the original. This gave me a connection on the trunked interface. THen I moved the second one over (trunked). Then I created 2 new vm port groups, one for each VLAN and moved the VM's onto them. Finally I deleted 'VM Network' port group from each host...
I am very happy now as we have much more capacity with the pooled resources and a lot more flexibility and redundancy.
Thanks again both for the help and I hope I made sense with the above explanation.
Cheers,
Chris