Thanks for your comments and suggestions guys.

I know that Xara has the option of being able to draw a SPIRAL.
But, that's not the same as the Fibonacci Curve.

And many thanks for the link (reminder) to the SPX Spiral Generator.
I did used to have that, but, I've downloaded it again.
But, whilst it looks as though it produces something that looks like a Fibonacci Curve, it actually isn't.