Priceline works very well on its bidding site for London - look at Bidding for Travel. You can get two rooms at the lower price. Hotwire lets you specify the number of people in the room so you can go there if you wish.
I agree, and use Priceline's 'name your own price' and/or Hotwire 99% of the time. In this particular instance, I need to book a specific hotel and can't go the opaque route.