I was "taught to teach" 85% of lift-off speed by 40% of TODR when I did my MEPL FI upgrade many years ago. The person who taught me this was a senior ex-RAF test pilot (known also to JD); I can't recall which of the performance documents it comes from but I recall stumbling-over the source again a few weeks ago. I can only think that it's in JAR-OPS because I (sadly) was looking through that recently. I would be eternally (well, until next week) obliged if someone could put me out of my misery and tell me where it is.
Of course JD is absolutely correct that there are many factors which affect the real world accelerate-stop distance, but if the manufacturer doesn't provide the data one needs something on which to hang one's hat.
HFD