Mr Hesketh, I can't answer your question, but, small world.... Welcome to Tableau
Thanks David, I hadn't spotted that but it is along the line of the things I have been trying. There are more examples of getting a date parameter in the example Adventure Works workbook.
With all of them I have the same problem. I can set up the date as a continuous date and add a measure against it, but this still doesn't provide access to the normal continuous line chart.
Looks like this is how it is with cubes...