Since I wasn't convinced by the likeness of my first attempt, I thought I'd give it another go.
This time I was really happy with the framework. If I decided to stick with just line drawing, I think I'd be OK!
But, instead, I persisted with more detail and shading:
Once again, the likeness was still missing, so I tweaked the chin and mouth a little, and voila!
It still isn't right, but voila sounds impressive ;) And, regardless, I think it's a better result than the previous one, so mission accomplished (in the Iraq war sense of the term...)