P Watts,
The FATO at EGLW is probably too small for the 109 helipad / vertical profile, just as it is too small for the S-76, so there's no guarantee that the pilot can reject and stop on it. An early forward transition is therefore probably less risky, at least "in the unfortunate event of", the aircraft should ditch level, rather than toppling off the end of the FATO and going in nose first......
It's about time Central London was better served by a larger site or a number of sites, including a proper facility at Heathrow and at Gatwick, but that's a different story.
