Recieved this look like we need to go to MCD4.2
AMC have come back to us and have stated the following
Since Desktop/Wireless licenses also include a Device license within its package, you cannot add any more Devices to this application record, as you've reached the 64 device limit (56 + 8 included with the base license). In order to transfer more licenses, you will need to order and add the following part number to app record XXXXXXX
54002541 - MCD: Integrated S/W Upgrade to 200 Devices.
54002541 MCD UPGD TO 200 DEVICE INTGD S/W PKG
It appears that upgrading to MCD4.2 will actually perform the license conversion changing them to Enterprise User Licenses, therefore removing reference to user/device.
If you do go down the MCD 4.2 route make sure you use the following software load updated on May 27th 2011. MCD 4.2 SP2 PR1 ( 10.2.2.10). It fixed a number of issues.
Let you know if it works?!?