Hi Alex.
Maybe it would be wise to take off a decent part of the existing foliage (leaving maybe half) while beginning to dig a trench around the roots and allow the plant redirect some vigour. Not sure if its the right time, from memory spring is good when there is a little more warmth than present in Melbourne.
I am no expert on Pieris hence the caution. I expect that they as a species do bud on old wood but I don't know what sort of shock uprooting and loss of foliage would give.
I have moved them from place to place in gardens by maintaining a rootball while pruning extended roots and balancing this with foliage pruning and shaping. The results have always been good, Pieris prove to be good subjects.
There has got to be someone hangin around that can give better advice than me on Pieris though
