from Heathrow to Marble Arch

Sally: If you take the Tube all the way, you will have to make at least one change, as Marble Arch is on the Central Line (Heathrow to Holborn on Piccadilly, backtrack to M Arch), and more likely two (at Hammersmith change to District/Circle, change again at Notting Hill Gate). That means a lot of stairs and/or escalators to negotiate while carrying luggage.
You will be jet lagged and generally weary, and it will be your first time in London. I would take the train to Paddington (take the Connect rather than the Express if you want to save a little money, as it is half as fast and half as expensive), then a taxi for the short ride to your hotel. Others may have other opinions, but for me the ease of this outweighs the monetary savings of the Tube. Keep in mind that you can buy and print out tickets for the Express/Connect at home, which would save time when you get to Heathrow. You are going to have a wonderful experience! London is one of the very greatest cities in the world...enjoy!

I agree, take the Heathrow Connect to Paddington Station then a taxi to your hotel...especially if you have large luggage it would be easier for you and you would get into London sooner. Not knowing your age, if you are younger then making changes on the tube might be fine for you, but it does take a hour by tube.

Take the Airbus, it works great and there is a discount for rdtrip. I think it is Airbus 2, ck to verify. a little more than tube but convenient imo.

This exact same question was discussed on this site about a month ago. Preponderance of suggestions was train to paddington, taxi to your marble Arch area hotel. Once you are familiar with the Tubes and their stairs /excalators you may be comfortable doing the Tube on your return to Heathrow. But I would still do taxi to Paddington and then train to Heathrow. The Tube changes to get from Piccadilly Line to Marble Arch are a hassle without luggage. (you need to have travelled them daily at rush hour to understand what I am saying- not just look them up on a map) i do suggest you search for the earlier discussion on this subject and get all the discussions

After an overnight flight from the States, I recommend taking the Heathrow Express or the Heathrow Connect to Paddington and then catching a cab. Taking the Tube saves a few dollars, but I don't think it is the way for jetlagged and sleep-deprived first-time visitors to begin a London visit. Frankly, anyone who can afford a London visit from the U.S. can afford to take the Heathrow Express and grab a cab. Skip a couple lattes and you'll be even. If you haven't, you might want to contact your B&B and ask if you can get in your room when you arrive, which will be just after lunch. People sometimes have trouble finding the taxi rank (queue) at Paddington. If you are facing the tracks, it's to the left, down the platform a bit. There are lines embedded in the floor leading to it. If there's a queue of people, just wait until you're at the front. Won't take long.

My advice is to avoid burdening yourself down with too much luggage. Large bags packed with more clothes than you end up wearing are backbreaking to carry around. You probably will wear only half of what you take. See Rick's travel tips on this website. I still pack less than he advises. Since this is your first trip to London, I thought I'd mention that.

Thanks for your help and comments! We hadn't a clue about the Heathrow Connect but it seems the way to go for us. I think the comments on the tube were spot on. We're in good shape for a couple of 44 year olds but the thought of being tired, disoriented and having to deal with luggage on a subway was not appealing. Thanks again everyone!

Sally, I haven't taken the Heathrow Connect, but the Heathrow Express has racks for luggage storage, if that's an issue for you. Advice to pare down luggage is well taken. It's a pain shepherding bags around Heathrow, and collecting checked bags will only prolong your stay in the airport. And, frankly, you can easily not have enough space in your hotel/B&B to easily stow them. London hotel rooms are small by U.S. standards.