My AV stuff is sitting on a shelf in an alcove in my living room. At the moment, it's a complete rat's nest of cables. I've managed to mostly tidy up the cable runs by drilling holes in the shelves and having the cables run up near one rear corner. The problem is the excess cabling behind the AV receiver, PS3, HTPC, etc.

I'm looking for ideas for hiding it.

Of course, I'm in the UK, so my house is made of solid stuff, so suggesting I punch a hole in my drywall and use fish tape is going to get you nowhere. In my case, the wall is made of concrete block. I'm wondering if maybe making a false plywood back wall to the alcove would work. Has anyone done something like this? Got any other tips or ideas?