Aside from the billboard's location, I suggest there is another issue for the industry in London to consider.
I think it could ignite renewed interest by LE and municipal officials in adult activities not just for FW but, for all of London. Seems they're already doing it as these current lfp articles suggest.
http://www.lfpress.com/2014/02/19/lo...an-trafficking
http://www.lfpress.com/2014/01/28/lo...h-sex-offences
http://www.lfpress.com/2014/01/28/ch...an-trafficking
Now, I know there is a big difference between how many of the lovely EC Ladies conduct their professional affairs and a traffiking situation but, all it takes is something like a bold public ad of any kind by anybody to ignite an extensive investigation into the London industry. Let's be honest. Traffiking does and is happening. LE would be well within their mandate to investigate to what extent. As they should be.
I don't want to sound paranoid, just saying things like this billboard, beyond its debatable location, could cause some unwanted situations for all concerned and, we need to realize the possibility.