The one at Nine Elms has already been confirmed in another thread as the construction hoardings with the hotel's name - Park Hyatt London at River Thames - have gone up along with several floors of the tower, and the 5 Strand one has been bandied about for a while as well. Planning documents for that one have "Park Hyatt London" explicitly mentioned on there, and with demolition of the existing building on the site having commenced I'd wager that that project is also confirmed.

khabah