I own a 7-year-old Mercedes CLK 230 Cabriolet with 62,000 miles on the clock. I don't think it's worth that much now, but would like to keep it as it still looks quite good. Is there any point in continuing to have it serviced by a Mercedes dealer at expensive labour rates, or would it be better value to use a cheaper, reputable non-dealer garage? I only do 20 or 30 miles a week in it these days, but give it a longer motorway run out every month. Most of the time it sits on my drive.