If you refer to a similar concept of " safely" continuing the "0/0" type take off as commonly used in other prescribed and approved techniques.....it would be determined more by performance capability considering a failed engine at any point in the take off and the height of obstacles in the take off path.
Such take offs are very rare...excepting night offshore and article or desert operations.
The technique I learned was to ascend "vertically" using a "hover" attitude....until clear of known obstacles the adjust the pitch attitude to achieve Vbroc until 500feet AGL then use the desired airspeed/ROC/power setting desired.
Mind you we were doing these in UH-1's, H-19's, H-34's....single engine helicopters....two of which had Manual throttles.
So continued flight post Engine Failure was easy decision!
Consider in this accident....the visibility (lack of....) prevented a safe takeoff using any approved takeoff profile. The right profile was no take off under the circumstances.
Perhaps the U.K. Rules need examining!