Well I got round to doing one side over the weekend:-
All in all cost per side is just under £14, the mygti guide covers most of the points, although I didn't solder my connections as I don't have a soldering iron, so I just used scotch lok connectors.
The only other point worth noting is that the repair wires aren't long enough so need to be extended about 5-6 inches, I had a spare repair wire so used this.