Specifying tick_labels for non-categorical data produces unexpected results.

A user may specify tick_labels for non-categorical data because they want to display units or convert the raw values to something more readable (eg percentage (50%) rather than the proportion (0.5)).
Currently, if tick_labels are specified, the function will assume that you are defining categorical data. This may result in unexpected behaviour such as moving the tick_labels to the centre of the ticks and/or disabling contour mapping.
The requested behaviour is to change the labels of the ticks without modifying these other things.