Non-Stop, Overnight Flight arriving @ 8:00am into Heathrow-What do we do that first day in London?

Daylight, that's the answer. Resets your body clock. Sunshine, if any.

I see from your question that you are arriving at 0800 GMT. That tells me that you will be traveling in winter or the winter side of autumn or spring, when the nights will be long and the days short. If you had traveled in the sunnier time of the year it would have been BST.

When the days are short and the light is gloomy outside is even more important to reset those body bits to help you over whatever jetlag you may encounter...

What Nigel said.
The hotel may not have a clean room for you in the morning, but hopefully they will at least store your bags.
If they don't have a room for you, you won't be able to "freshen up." Ask them when is the earliest they will have a room for you.
Even after you get into your room, freshen up but avoid the temptation to take a nap.
I would not see a play that first night, because you will probably be feeling really tired after dinner time. The usual advice is (for the average traveler, whoever that is):
stay outdoors, if the weather permits
keep moving with light exercise but nothing strenuous.
Jet lag is different for each traveler, these are just suggestions for the average person. The favorite routines for one traveler may not work for you.
Don't do anything potentially dangerous like driving a rental car.
Try to stay up until a "normal" bedtime, London time.

I will second Kent's suggestions - don't nap, stay outside or moving around, don't plan anything challenging, and don't plan to see a play. Even if adrenaline carries you through the day, it won't be long after dinner when you feel the effects of the time zone changes and you will want to be in bed early. I travel frequently and, while I am not really bothered by fatigue all day, I am still ready to get to bed by 8:00 or so (which pretty much coincides with the start time of a play). That would be a very expensive nap.

Do note what Kent said about suggestions being for the average and may or may not work for you. I had always pushed myself to stay awake, then last year arrived about 230PM in the pouring rain. It was so yucky I did not really want to go out, so wound up taking a nap, woke for some snacks for supper, and then back to sleep til the next morning. I DID miss doing anything the afternoon of arrival but I had no problem after that. It surprised me because I was expecting to be jet lagged for a couple of days because I didn't follow instructions, lol! You may wind up wanting to take a short nap in the afternoon when you can get in to your hotel room...or not.

Usually I like to walk the hotel neighborhood and then to one of the big parks. The last few times I've stayed near Victoria Station so I walk to Buckingham Palace and then on in to St James's Park. Look and see what is in your "neighborhood". I would not do a museum or see a play on arrival day just too indoorsy.

You can also consult your physician to see if she/he would recommend and prescribe one of the short-term medications that are available to help you deal with the symptoms of jet lag.

Hi. If you are arriving at 8 AM, expect a couple of hours in Heathrow, then however long it takes to get in the vicinity of your hotel. Try to check in or at least leave your luggage. I like to plan my first day. I do try to stay active. Some of the following are things I have done:

• participate in a London Walks tour not too far from my hotel
• identify a landmark or destination I really want to see - last time I made it to Westminster Abbey at opening time; one time it was a long trek to the Tower, sometimes shopping at Liberty; sometimes a favorite bookstore
• catch a matinee at the Globe
• always identify a mini market or supermarket in the vicinity of my hotel - since I am often solo, my first evenings frequently include a sandwich that appeals, Pringles (never eat them at home), chocolate, some bubbly, perhaps a favorite British magazine; if the hotel has take-out, I have been known to order pizza; I have also eaten at cafes at museums or other destinations

Once I am back in the hotel, maybe around 7, I clean up, sort my paperwork for the next day, read, eat, listen to the telly, in general, just take it easy. I often go to bed fairly early, say by 9. It doesn't bother me to wake up in the middle of the night and watch late night British television. It can be fun.

I recall one trip when the following day (day 2) I had tickets to the British Museum around 10 or 11. I just slept in. It was luxurious. I don't often do that, but I remember how well I felt that one time not tied to an alarm clock.

So, your trip must be yours and will be unique even among other trips you take. What it is you are hankering to see and do can drive your first day. PS, I would not recommend a play at night. I went once to evensong at Westminster and almost fell asleep on my feet. Even a matinee can be challenging since one is sitting for a prolonged time.

Once you've left Heathrow in route to your accommodation take stock of how you feel and base the remainder of you first day on that feeling. As noted your accommodation may not be ready for your early arrival so freshening up may not be an option, a jolt of java will be and hopefully you'll be able to locate a Costa Coffee, Nero Coffee or Starbucks in your neighborhood. Totally agree best to get outside in the elements to walk off the inevitable jet lag. I'll repeat what I've offered as a suggestion to first timers about what to see on Day 1. Here it goes. Pretty certain you won't have gotten your Oyster cards yet so Google the address of your accommodation now to see where exactly the closest tube stop is. After you've dropped off luggage, walk to that station, get your Oyster cards at a manned ticket window, pick up the small invaluable pocket size tube maps that are usually on the counter or ask the attendant for one. Once you've completed your transaction and have your Oyster cards ask the attendant which line you want to use to get to the Westminster station. Dependent upon where your accommodation is located this might be involve changing trains but no matter. You'll discover what great transport the tube is for seeing London and with color coded lines and definitive signage how easy it is to use. When you arrive at Westminster Station, exit the train, Mind The Gap, and follow signage to Exit 1. Walk outside. In front of you will be boat piers, the Thames, the London Eye across the Thames to your left and Westminster Bridge to your right. Turn to your right looking towards the steps up to the street then look up. Smile. Climb the steps and begin your first day in London. That's Parliament square. Parliament, Big Ben, Westminster Abbey. Easy to walk from there up Whitehall to Trafalgar Square or up Birdcage Walk through St James Park to Buckingham Palace or across Westminster Bridge to the London Eye. Your choice. Before you depart and to help you orient yourselves take time to use Google maps Birdseye view of London. Type in Big Ben, London, United Kingdom in the search box and then use the directions options and the walking icon to figure how far you are from places to wish to see. Can you walk to it or is it best to take the tube or a bus? .I do like the idea of joining one of London Walks that evening. Informational, varied options depending on your interests and inexpensive for London. Fun as well. Or you can simply locate a nice pub, cafe or restaurant in your neighborhood, dine then head "home" for a good nights rest. Have a great trip to a great city!!

When are you travelling? We are currently on British Summer Time (BST) not GMT so you maybe an hour out! BST lasts until the end of October.

I will be in a similar situation - arriving early in London.

Jet lag is hard on me, but I plan to leave my bags at the hotel and then get an orientation on a double-decker bus tour (hop on - hop off). Ticket includes Thames river ride. Do some walking and adjust the best I can by trying to stay up until the early evening.

When traveling to Europe, I prefer to get into my destination city as early as possible. I stop by my hotel to drop off my bags(If by the off chance my room is ready, I freshen up but never nap). After my hotel stop it's back out into the fresh air. At lunch time I stop for a light lunch. At check in time I head back to my hotel and unpack and freshen up a little (if I didn't get the chance earlier in the day) and head back out. When dinner time approaches, I find a place to eat and by 8-9 pm I'm ready for bed. I find I sleep like a rock that first day and wake up refreshed ready to start my trip.

We just returned from a London/Paris trip with a similar arrival. Best thing for us was walking from our flat up Piccadilly, and then through Hyde Park, watching swans & people, letting the sunlight reset our body clocks. In July, the open air hop-on buses would be a great intro to the city as well.
Know that from Heathrow you are very close to Windsor Castle and you could be there when it opens to tour. It is very impressive with all the pomp & pageantry that you expect from a royal castle. You would easily make it to your hotel in the afternoon.

We do this every year. Our flight leaves from Dallas around 4 PM, 10 PM London time. I set my watch to London time and it helps me to realize how late it is. We have our dinner and a drink around 11 PM London time. The very fact of setting my watch to London time makes us realize it is time to nap. Yes, we do have troubles keeping asleep, but at least we get 4-5 hours so we are not so tired upon arrival. We take the Heathrow Express to Paddington then a taxi to our hotel, leave our luggage, and take the tube down to Trafalgar Square. Wide awake, we enjoy the surroundings and have a bite to eat at Gordon's Wine Bar or Covent Garden, mill around , then repair to our hotel around 8-9PM. Jet lag does not keep us from our appointed rounds.

Hi,

The best time to arrive at LHR is in the morning (for me after a 10 hour non stop flight from SFO), when encountering short lines at Border Control is most likely, getting to the B&B or hotel and dropping off the luggage off. You're almost starting a whole day in London. Upon arrival jet lag may take a toll on you, or it may not even hit you...just depends. Not everyone is affected by it. I don't. Have a nice lunch, go to a museum, go to the theater area or Chinatown, I prefer a museum and strolling in a park (Hyde or St James), etc.

I would suggest one of the following tactics:
Ask you doctor for a sleep aid such as Ambien. I take an Ambien as soon as they put the meal in front of me on the plane and sleep all the way and wake up fresh and ready to go, no jet-lag. BUT, I would advise you to try it before you go. The medication effects people in different ways.

If you don't sleep all the way on the plane, I'd try walking along the Thames, riding the London Eye, maybe going to Greenwich and seeing the Cutty Sark and the Prime Meridian. Have a good dinner at London dinner time and go to bed. Stay outside in the sun (what you can find) so your body clock readjusts.

Good Luck and have fun! You'll love London.