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!