interesting that Henderson also thought it might have been a try and also that he didnt think either the touch judge or referee had ruled it out. Are you sure that it was a definite rule out?

It obviously was a Def rule out as it was not awarded and they went back to the penalty, the ref actually followed the ball and only went back after play stopped.
If the try had been scored it would have been awarded and the foul play then dealt with

My point is that Henderson made the same point as me, there was'nt a decision - merely a look at late tackle? It makes no difference to the score or result, but i still felt they didnt rule - Williams would have had a hat-trick as well!

Not sure what you mean by decision, the ball was dead, no try was scored, what decision was there to make, the foul play dictated what the restart was.

Did the touch judge put their flag up at any point?

Sending off sufficient no charge.