it is actually a decent gym chain with a good selection of weights for central London standards. They also have a good boxing and martial arts section (some decent boxers and some UFC fighters train at their Holborn branch). They were a bit unlucky with the timing of the opening of their newest branch, in London's banking district - just in time for the banking crisis. Converting the building (which used to hold a giant bank vault) to a gym must have cost them millions.
So this is just another desperate attempt by that branch's management to stay in the news.