Hi all, I tried the above yesterday and found what I think might be the factory method for adjusting the handbrake. It's WAY easier than taking off the panel with the four bolts.
Just in front of the panel, in the bottom of the radiator hose cover/box there is a small rubber cover about 2 1/2 inches square. That pops out with very little effort and is directly under the adjustment nut for the handbrake. There is enough space to get your 13mm spanner onto it easily and if you use a ratchet spanner the job takes about 5 minutes including jacking and propping the car on an axle stand.
I found it by accident after I had taken off the bolt on panel, undone the gear linkage, dropped one of the handbrake pulleys on the ground, etc, etc.