That's not the whole story - the pedestrian has right of way as soon as their foot touches the crossing. However, the rules for drivers suggest that drivers ought to be watching for people about to cross and prepare to slow down or stop. See the Highway Code link here for details.

The driving instructor in this case sounds like a charmer and a true knight of the road.

Personally I wouldn't recommend any action which might antagonise someone who's speeding through a crossing without a care - my experience has been that they're either too careless to notice, or too aggressive and selfish to change their ways.