How to take the Train, Tube or Airport Shuttle from London, Heathrow to Bloomsbury

There are several options, but the one you mention, taking the Picadilly line to Holborn is the easiest (no changes), the cheapest, and despite the fast Heathrow Express, since the tube is direct, probably the fastest.

At the station in Heathrow (exit the secure area after immigration and baggage check and follow the Underground signs) there are machines and staffed windows where you can buy either your Oyster Card or a single ticket.

For Oyster card, you actually have two options, the 7 Day pass you mention, or just buying one that you load with some amount and top off when needed. If you buy the pass, it likely will be for Zones 1 and 2, so to use from Heathrow requires paying a supplement, if you buy the other, the cost is just deducted from the total. Consider how much and where you will be traveling, remember that the pay as you go maxs out at 9.80 GBP each day, so if you will be using the Tube a bunch, that is your daily cost, otherwise, it could be less, or you may not use at all. Consider also that your dates are longer than 7 days...so the conventional Oyster card may be better.

As for returning to Heathrow, Yes, just go to Holburn and catch your train. Do be aware that not all trains go all the way to Heathrow, or to all terminals, signage will state where each train goes, you may have to let one or two go by before the right one comes along. There will be regular service on New Years Day, less frequent maybe, but service. Take a look at the very good www.tfl.gov.uk site for more information as well as maintenance shut downs.

The daily Oyster Card cap is currently £6.80 when you don't go outside Zones 1 and 2, which is likely to be the case most days. Whether loading a weekly pass onto the Oyster Card will pay off may depend on how big a walker you are. You're staying in quite a central location, and it's possible you'll only take the one airport trip on your arrival day as well as your departure day. I suspect it will be a borderline call.

I believe you will encounter some stairs at the Holborn tube station.

I'm rushing now and can't address all your questions. But if you do decide to use a 7 day TravelCard and load it on to an Oyster, you will most likely only want a TravelCard good for zones 1 and 2. You can then add Pay As You Go credit to cover any travel outside zones 1 and 2. Note that only a few common tourist attractions are outside these two zones, but there definitely are some, like Hampton Court and Kew Gardens.

Heathrow is in zone 6. I arrived after rush hour, so it only cost me an additional £1.50 on my 7 day, two zone TravelCard. I don't know the current price for rush hour. Since I took no other trips outside zones 1 and 2, I just added £1.50 when I bought the card.

When you arrive at Heathrow, just follow signs to the underground station (it's about a 10 minute walk from terminal 3). There are uniformed helpers who will assist you in using the ticket machines. Just figure out what you need beforehand, since in a jetlagged and tired state, you will want to know exactly what you want, and can then ask them for the correct product.

TFL has a couple of different ways to provide disruption alerts, but the best view of the planned holiday calendar is at https://tfl.gov.uk/status-updates/major-works-and-events/christmas-travel.

Thanks to everyone! You all provide amazing and detailed instructions. Just what a jet lagged person needs.

One clarification, would the cost for the tube from Heathrow to Holbrook be around the $6 to $10 range?

Thank you, everyone again. Such wonderful gestures of real help!

Unless you never plan to take any other tube or bus rides during your trip (a very unlikely prospect!), you won't want to buy a single ticket for your airport ride. You'll either want a 7 day TravelCard (to which you will add a small amount for the Heathrow rides, as I described above), or you'll want a PAYG Oyster. In either scenario, the cost of the ride to and from Heathrow will not be $6, or even its equivalent in £ (GBP).

If you're using a PAYG Oyster, you'll just load it with some money. The card costs £5 to buy; put £30 on in addition when you buy it (again, there are uniformed helpers at the machines at most stations to help you with this). You then "tap in" to get on the tube, and "tap out" when getting off (this tapping is what opens the turnstiles - watch others and imitate). For buses, just tap in on entry; don't tap again during your ride or when exiting the bus.

The Oyster system keeps track, and not only charges you the correct amount per ride, but applies the correct "cap" (maximum fare) at the end of each day. This means that you will not be charged more than the one day TravelCard fare for the zones you traversed that day. For zones 1-2, that's currently £6.80; for zones 1-6 (the days you go between Heathrow and the centre) that's currently £12.50. Again, this is the maximum you can be charged; if you take fewer rides, you'll be charged less. And again, you don't have to think; just tap in and tap out, and the Oyster computer does the rest. This is a big advantage over most transit systems, where you have to figure out in advance if a day pass is worthwhile; in London, you get the day pass price if take enough rides, and pay less if you take fewer rides.

I agree with Emma, that since you're in London on a Christmas Day when there is no mass transit to use, just get an Oyster with PAYG credit. If it runs low, top it up at the machines in all stations.