So that's what we did... I hadn't got back to my guidebook to try and work it out yet.
In Will's picture I guess the green circle is the DBB at the end of our P1 and the blue circle is the DBB where we finished P2. The slab directly above that to the solid bushes (with the abandoned abseil sling) at the base of the final corner is our P3. And our P4 ended at the red circle.
I'd say P1 was about 55m. P2 about 30m. P3 about 25m. And P4 about 45m. So a rap point in the red circle would not get you back to the blue circle unless you had two 70m ropes.