Thanks Mad (Flt) Scientist
I think I have since come accross the answer I was looking for.
I believe that the Take off is from the start of the take off roll to screen height.
You then have the Net Take Off Flight Path which is divided into 4 segments:
1. Screen Height - undercarriage retraction
2. Undercarriage retraction - flap retraction
3. Level acceleration (during flap retraction)
4. Climb (clean) to 1500'
segments 3 and 4 can be combined.
as usual I am probably wrong.
