Like most non-US Worldcons, Loncon doesn't have one or two mega hotels attached to its convention centre. Instead, there are a bunch of smaller hotels scattered around the place. And the ExCel Convention Centre is vast to begin with. There is no "main hotel" or "party hotel," because parties will not be sanctioned in hotels, being confined to the convention centre. However, there is a "closest hotel," the ALoft, which is a mere 50 meters from the east door of the ExCel. Because of the anticipated high demand on the ALoft, you can't book directly with that hotel. Instead, you have to book a room at one of the other hotels, then enter a lottery to have a chance to reserve a room at the ALoft; if you win, you can release your other booking.
By the time I remembered it was Booking Day, rooms at all of the other relatively close hotels were either full or showing prices higher than I wanted to pay, so instead I opted for the Crowne Plaza, which is an Intercontinental hotel (Holiday Inn group) with which I have my Platinum status. It unfortunately is 950 m from the end of the ExCel where Worldcon is happening, which means we won't be popping back and forth a lot. OTOH, the Docklands Light Railway runs right next to this area, and there are stops near both my hotel and the east entrance of the ExCel. It might be worthwhile to load a 7-day Zone 3 travelcard (unlimited travel in this area) onto my Oystercard for GBP24; that makes a break-even at only one or two trips a day, and the DLR runs every 8-10 minutes most of the day.
Anyway, on to the booking. To my amazement, the range of dates I wanted (arrive Wednesday, depart the following Tuesday) was already sold out, although Monday departures were still available. I went ahead and booked the five-night stay and let Loncon Housing know about it. I got a note back from the housing agency saying that they're working on getting more "shoulder" nights and that I should be able to expand my reservation later. In the meantime, I directly booked a one night stay at the same hotel through the IHG website. I don't like having end-to-end reservations like this because there's always a risk the hotel might want you to physically switch rooms, but this seems like the prudent thing to do. If the shoulder nights open up, I'll expand the original reservation and drop the one-nighter. If the shoulder nights do not free up, I'll probably go ahead and rebook that one-nighter using points, as there's no real need to spend that GBP130 when the convention doesn't get any credit for it. I have (or will have) enough points that I could almost book the entire convention stay on points, but I'd rather not deprive the Worldcon of nights toward their room commitments, having sweated out making the room block from the other side of the fence for more than one convention.