First time in UK, excited to see as much as possible in 3 days so I don't want to waste a single moment. But with the early arrival and the fact that it's really midnight for my cicadian clock, I'm not sure on what my options are at such an early hour. I'm guessing a take the tube to my hotel and drop off my luggage and statr exploring the city. I would like to hit a great tour of the city that gives me a good basic understanding of the layout of the city, any thoughts on that? Thanks

First of all, get the idea of what time it is back home out of your head. Thinking about what the "real" time is will only mess you up.

I think the best thing to do is to take a hop on, hop off bus tour which will give you the highlights and a nice overview. And don't be afraid to actually get off and stretch your legs at one or two of the places.

Is there a variety of tour companies or are the red double deckers are operated by the same company?

The hop-on hop-off tour bus companies are www.bigbus.co.uk and www.theoriginaltour.com.

Believe it or not, kicking back with a cup of coffee or over a decently-prepared and served meal once you store your luggage at the hotel is not necessarily considered "wasting a single moment."

...and enjoy a full English breakfast with bangers and beans to get you in the spirit, and fueled for a day of sightseeing! (Here is where I defer to my cicadian clock, and also enjoy a pint of bitter, too, but that's just me!)

sitting down for a bit , having a coffee and a meal is a good idea!
Also try to stay in the fresh air ( boat tour on the river, open tour bus, Hyde park, the Kensigton Gardens etc) rather than going into museums and galleries the firs day.

Stay outdoors as much as possible. After we check into IBIS NORD in MUC (O'Fest), we cross the street to the big beautiful cemetery and walk around with our wine and get as much sun as possible.

I second the notion of a bus tour. Either the original bus tour or big bus company is fine. Great way to get acclimated to the city and stay outdoors. Take a 1 hour nap midday then make yourself get up, shower and go out to dinner. Go to bed at normal british time and next morning you will be fine.

My son and I just did the same thing except we arrived at 7 AM. We were fortunate as to when we arrived at our hotel our room was ready. We had a quick breakfast, went to our hotel and slept for a couple of hours, showered and were on the double-decker (by the Original Tour) by 3. It was great!
If the room had not been ready, we had planned to go straight the d-d bus tour.

Since most of my arrivals to London arrive in the early morning on overnight flights from SFO.I usually check my bags at the hotel,have a full English Breakfast,and then go on a "Original London Walk."This keeps you outdoors and on your feet for at least a couple of hours.Resist the urge to take an afternoon nap or you may never get up again that day.
http://www.walks.com/

We always land early in London, and after checking in our hotel we go to breakfast. We're always starving, no matter how much we eat on the plane, and it uses up a bit of time until things open up. Then we walk around, window shop or something else outdoors. Going to the Westminster area is great - seeing Big Ben, the Houses of Parliament, Westminster Abbey, the Thames and the London Eye - it all says "London"!

Like keefmick, we take a 1 hour nap (maximum - you have to make yourself get back up) in the early afternoon. We then make it through dinner and a regular-ish bedtime in our new time zone.