The correct way to sort any handbrake problem is to ensure firstly that the shoes are free to move on their pivots, and at the same time check that the rear wheel cylinders aren't rusted solid - you can check these by tapping the shoes to and fro to see if all is well. Next its usually best to slacken the handbrake cables off a bit, and allow the self adjusters within the brake shoe mechanism to do their work - often they need a bit of help though, depending on the design. Its only at this point do you adjust the handbrake cable, and check that there is an even pull on each rear wheel. Any friction in the cables or on the shoe operating mechanism is greatly magnified, which manifests itself in a poor handbrake. I think the garage is correct by saying that they have to clean everything up for inspection, but at your fairly low mileage I wouldn't expect any problems with the wheel cylinders or brake shoes. I would normally charge 1 hour per side to sort this.
John
March 2008