flytta en stor rhodedenrum

Translated this asks- Has two medium-sized rhodedenrum that we want to move! How big a hole do you dig, diameter and depth? Should any roots pruned? What is needed as fertilizer?
I found this by Helen Yemm in the daily Telegraph:
Rhododendrons: a midsummer move
I think you can look on this optimistically. Rhododendrons (and azaleas) move easily, and I hesitate to say it for fear of getting howls of disagreement from the unfortunate few who have botched the job, but midsummer is as good a time as any.
These shrubs have a compact and much shallower root system than you might imagine. A further plus has to be that this plant is not going far - it is moving to a garden with presumably the same general soil type and pH as it is used to and will spend little time out of the ground. What's more, this specimen is not large in rhododendron terms.
Prepare for the move by asking your neighbour to give the roots a long slow drench (rainwater preferably) a few days beforehand. Also, prune the shrub by about a third, removing the old flowers plus a foot or so off the ends of most of the branches. This will make it easier to manoeuvre and also reduce stress to the root system.
On the day of the move you will need two able-bodied people, leafmould, some granular plant food suitable for acid-loving plants, water and a large sheet of tough polythene.
First, make some investigatory probes with a spade all around the plant, roughly halfway between the extent of its (former) canopy and its main stems to find out how far the roots extend.
Once you have established this, dig a hole for it in your own garden about 18in deep and a little wider than the width of the root ball. Fork some leafmould and a fistful or two of fertiliser into the hole and water it.
Dig up the plant and manoeuvre it on to the polythene sheet and lift or drag it to the new site, plop it into the ground and water it in well before backfilling around the roots with a mixture of soil and leafmould and firming down the whole root area with your boot. Apply a leaf mould mulch.
New growth will gradually appear, but the plant will not be likely to flower until 2013.
Good luck.