1.Vertical symmetry plus smooth stroke with both sliders set to 65. This puts a delay on the line and you have to watch where the line is going rather than the cursor. It takes a bit of getting used to but produces good results.
2. Coloured.
3. Filtered.

Now that is a really neat tool so thank you Erisian; I've never used it before but will now have a play.

The lines are indeed smooth (i.e, almost Bezier like), Erisian. Like the final result you came up using your drawing as well.

Thank you both. I have to say to anybody that wants to try this that if you want sharp points, you need to start a new stroke otherwise the weight of the smoothing will give you curves.

i can see it easily can be copied and rotated into an interesting Mandala.

Could be. Or you could start from scratch using the mandala function instead of symmetry.