Fantastic. Many thanks PJ.
Having already reviewed a set of Mullard data sheets earlier today, I felt a bit embarrassed when I checked your pg. 9 and saw the curves. I didn't understand how I could have missed that. But rechecking the Mullard sheets that I had found, there are no curves for the tube in triode mode, just a table of triode operating points and a triode "performance" graph that appears to plot current, voltage and distortion against power output. Lesson learned!
cheers,
Derek