That's the one matey! It does seem to be the relevant post and mine is also located behind the lower passenger side dashboard. Having removed that, you can see the fan motor and the resistor pack is behind a small enclosure with a connector plug on top. You remove the two screws and the whole thing lifts out.
Some people have found it behind the heater controls switch panel, others under the drivers side of the dashboard. I kind of hoped there would be some uniformity in the location but it doesn't appear so. A replacement resistor pack is about £14 on eBay and hopefully this will fix the problem. This method of controlling the fan speed is very common amongst all vehicle manufacturers as it's cheap and cheerful. Problem is the resistor gets hot and fails very frequently so nice little earner from the garage who were going to charge £89 to fix it!!