a4 rear swaying round corners

[sbt]

hi i have recently started to notice a swaying sensation from the rear when cornering on bumpy roads. my car is an a4 1.9 tdi x reg avant it as covered 145000 miles but apart from this problem runs ok. i think it could be the rear axle bushes. as any body got any expierience of changing these ie is it much of a job how much and where from any info would very welcome