If your hotel has Sky Sports you will get three live games on Sunday night, one after the other. Also, if the hotel uses Sky as its satellite provider (as opposed to Virgin) you will have the option of watching an alternate game for each of the three slots if you don't like the one they have chosen. They usually choose the most exciting/important games to show which means that if the Skins are still in playoff contention they will probably be on as the Skins and Cowboys are popular teams over here.
A number of London hotels and pubs also carry NASN which will show live games. Here is a list of London pubs that have NASN (use the same site for a list of hotels):
NASN - The Home of North American Sports in Europe
The biggest bar that will show games is the Sports Cafe. I would highly recommend that you book a table (ask for a booth with its own TV) if you intend to go there as it makes it a much better experience. Read the following for more info (this guy didn't have a table and although he complains about prices you had better get used to that in London as it is probably the most expensive city in the world and makes NY look cheap):
London Best Bars and Pubs
Finally, bear in mind that due to the time difference you will only get to watch the early games in a pub and will have to rely on your hotel for the later kick offs. Fortunately the Skins Cowboys game is early. Check out the Sky Sports site closer to the time to find out which games they are showing.
Sky Sports | TV Guide