I got the same story from the main dealer who does my servicing, and the reputable independant that I went to.
There are two axle types fitted to the Mk4. One has replaceble bushes, which are a press fit. The price for this was £280 plus VAT at the main dealer, £180 all in at the independant.
The second type of axle has hydraulic bushes which can't be replaced, hence the need for a replacement axle.
The idependent tells me they haven't yet come across a replaceble type yet !!!
Given that fact, I'm hoping somebody out there has come up with a cheaper alternative.