Rather than repeat myself in this Instructable, I'll just include where the new TV wall differs from the the first.
Step 1: Building the frame
The horizontal braces were fitted to match the width of the TV bracket, and small recesses were cut into the bottom of the frame's sides so that it would fit around the skirting board and be flush to the wall.
As this TV wall was to have a drop down desk, I first bought the piece of pine which would be the desks surface and made the frame the correct width to house it. You could of course do it the other way round, but I wasn't looking for any extra work!
Step 2: Boxing in the frame & fitting the desk
The desk is solid pine and is attached to the horizontal support using two flush-closing hinges. The horizontal support for the desk is fitted further back inside the frame, so that when the desk is in its upright position, it is flush to the front.
To support the desk when it was down, two small curtain-wire eyes were screwed into the top surface of the desk, and two to the downward edge of the upper horizontal support. I used braided steel wire for the supports as the pine desk is pretty heavy.
I also put an extension lead behind the TV bracket so that there would just be one plug coming out of the side of the frame, and I hid an amplified aerial behind the hardboard panel below the bracket for improved reception (sorry for the lack of photo).
Step 3: The 2 inch thick PC!
Working in IT and being a geek when time allows, I luckily I had some parts from an old Media Centre PC and a few I had hoarded over the years. After putting together a rough machine I then had to flatten everything out as much as I could. Luckily, everything fired up on my first go.
Step 4: Casing the PC
After cutting the pasting table to be the same size as the bottom panel of the frame, I set about fitting the PC into it. As the pc was going to be dropped inside the wall, all the fans had holes cut into the lid so that air could still circulate. I also fitted a large wireless aerial and made sure all the connections ran up to what would be the top edge of the case.
Step 5: Covering the frame
As any future wiring changes could easly be made with the desk simply dropped down, the panels could be screwed in and the wallpaper could be wrapped around the front and sides giving a very clean look. The underside of the desk was also wallpapered so it would all match when it was not in use.
Step 6: Adding the PC
The wires were then cable-tied to the inside of the frame, the PC was plugged into the hidden extension lead behind the TV bracket and a USB remote control was added so that the PC can be controlled with the desk up.