Is it possible to move a snapmirror destination volume fromone aggregate to another with disrupting the snapmirror relationships?
SEE THE SOLUTION
If you are using OnCommand, there is something called secondary space management wizard, using this you can migrate the snapmirror destination from one aggr to another without disrupting the relationship.
Great - thanks for this. Is this within OnCommand Core?
Yes, you can see this option in NMC. on Aggregates tab.