On the 2005 Wagen, you get at the two 20A fuses for the rear 12V plugs by removing the bottom of the dash on the driver's side. Here's a picture of the where the four T-25 (torx) screws are located after you pry off the fuse panel cover.
On my Passat the bottom left screw bracket was broken (NOT by me), but that doesn't matter as there's also a white plastic pinch bracket way under the dash panel that holds the panel tightly in place on the left (sort of where the white arrow points).
So after removing the screws, I pried the panel straight out starting at the top and pulling on the bottom next to that white plastic pincher. There's also some tabs on the top that help hold it snuggly in place.
Then just lay it on the floor and change the fuse like so:
The white arrow points to my blown fuse so I suppose the fuse next to it is the second rear 12V socket. But there's another one up at the top right; rear console 12V socket?
There's also a lot of mysterious, numbered, plug-in electrical boxes, but I restrained myself from unplugging them to find out what they do.
Anyway, it was all pretty simple and went back together without problems.
Hope this helps.