A couple of major points against rooftop helipads.
1. The UK CAA doesn't like them.
2. The cloudbase needs to be appropriately higher to land on the tallest buildings, not a good thing in central London.
As a regular user of the heliport and having seen the outline plans of this alleged new development, it seems to me that the continued existence of EGLW is now very much in jeopardy.
Seems to me that our capital city is pretty poorly placed when helicopter ops are considered. Even Heathrow and Gatwick are by no means helicopter friendly. It's probably going to get worse chaps....