Don't have docs to hand, but if you look in the Europe and Middle East Aerad supplement it has a bit on the different types of VASI/
PAPI in the front. It says all should be ignored below 200ft.
Also on AERAD Aerodrome plates, the little number in brackets next to the PAPI descriptor indicates the Minimum Eye Height above the threshold in feet. This will vary, even at places like LHR on the 4 runways.
JR