Had a hollow rattle/knocking noise from the rear of mine since nearly new. Over 22000 miles have played with seat catches, parcel shelf, boot catch, spare wheel/toolkit, different tyres, etc, but made no difference.

 

Having mentioned it a couple of times to my garage, they've just replaced the rear shocks absorbers, which there's a technical service bulletin for I believe (also affecting Mk 7 Golfs I've heard). Only done 200 miles, but noise has gone (hopefully once and for all !).

Hasn't made any difference to general road noise though.

The first batch were seemingly inferior, causing problems such as very bad riding etc. Skids didn't always replace them though. Think it depended on initial reaction of your dealer and what mood suk were in

Oops, skids is meant to be skoda