Have a stop over in London before catching Eurostar to Paris (will be back to London for last 3 days of trip). Should be at hotel by 15:00/16:00 pm. Any suggestions on sightseeing? We are staying near St. Pancras. I was thinking Madame Toussauds since so close and I can check that off the to do list. Any suggestions?
If I read your post correctly, it was about sightseeing, and not hotels, correct?
Re sightseeing: Yes, I would choose one site you want to see in the area before it closes (your pushing closing time there), and check it out! =) You might also want to consider catching a show in the West End, and just for the sake of ease, and the tight schedule, purchasing the tickets online for either.
If you have time that night (in lieu of a show), or the next day head toward the Thames. In about six hours, you can take a look around Big Ben, Parliament, Westminster Abbey, Admiralty Arch, Trafalgar Square, Piccadilly Circus, Buckingham Palace, and maybe have time to pop over to St Paul's.
Did that myself about 10 years ago. Didn't go inside anything other than Westminster, but was a great afternoon.
Hope that helps!
IMO after getting off a long plane flight fighting with the crowds in Madame Tussauds is the last thing I would do. However, might be a good idea if the weather is not good. As has been mentioned check their opening times.
If the weather is fine London is a great place to stroll around looking at the sights.