Thanks Deanne,
I plan to move all media assosciated with the "old" master to another media server prior to the master move.
Install afresh on the new master.
Then recover all catalogs to the new master server.
Issue vmglob -set_gdbhost "new master server" on all media servers
Then reassign "old" master server media to the new master.
This will happen in a mini test environment first so ist a bit of a suck it and see exercise.
Symantec have quoted 3 days for professional services to do the job. I reckon 1/2 day at the most !!