I was going to make a bracket at work out of some square steel tube, I'm not paying 100 odd quid for something I can easily make! I was going to attach 2 lenghts of tubing along the top and bottom of the tv, then attach the bars to the wall somehow.

I'm not sure what the difference between a stud wall or batterned block work, but its an exterior wall with insulation (same insulation as whats in my loft) then wooden studs and then the plasterboard.

I have used those fixings that spread out behind the plasterboard before in the kitchen, but for some reason my house has 2 layers of plasterboard so they wouldn't go in far enough to spread out and hold anything securely.