Pie Chart Data Labels Overlap

I have a series of pie charts with each chart having around 13 different data
elements making up the chart.
The data labels are set to show alongside the relevant pie sections -
showing category name, value, legend key and leader lines. Legend is not
shown.
In some charts the labels are spaced in the chart so that they are all
easily visible, however in others the labels cram on top of each other.
For all charts the label position is set to Best Fit. I have tried other
options when the labels overlap, but none of the options appear to prevent
this overlapping from occurring.
Is there any easy way that I can get the labels to space out correctly on
the pie chart?

FYI, I'm using Excel 2002.

Many thanks