You can't purchase NATIONAL RAIL tickets at Heathrow for trips that start on the Tube. The Tube is London's underground; National Rail is the rail system - like the difference between Amtrak and the NY Subway. You can buy Oyster cards at Heathrow

you won't be using what used to be known as BR [ie the train] if you get the tube from LHR to Waterloo -

take the piccadilly line, change at green park onto the jubilee line, get off at Waterloo.

try www.tubeplanner.co.uk

>>take the piccadilly line, change at green park onto the jubilee line, get off at Waterloo. <<

Or if you don't fancy lugging your luggage up and down stairs and along corridors, change at Hammersmith to the eastbound District Line (just cross the platform) then at Westminster (escalatora down to the Jubilee Line).

Or if your objective is one of the hotels in County Hall, you're going to have a bit of a walk whichever tube station you get out at, so you might want to just walk across Westminster Bridge from Westminster tube. At Wateloo, the obvious exit from the Jubilee Line brings you out on the wrong side of the station for County Hall, and you either have to walk right around or through the station, or follow the underground signs to the Northern/Bakerloo lines to the South Bank exit - probably easier to walk from Westminster.

or ask your hotel [assuming that what you're headed for] which the best tube station is.

it would help if you told us exactly where you are going. As explained, Waterloo station is one thing, some hotels near there could mean a different route.

We're going to the Park Plaza County Hall hotel, and the hotel's website does provide detailed directions on how to get there:

"From London Heathrow Airport (approx 90 mins)*

Take the London Underground
Travel Eastbound on the Piccadilly Line
Change at Green Park Station for the southbound Jubilee Line service
Depart at Waterloo and exit via the South Bank
Walk up York road towards The London Eye
After The London Eye, take the second turning on the left onto Addington Street
Park Plaza County Hall will be on your left


My query was more related to how to purchase tix at LHR. I gather from your generous replies that it's no problem to buy Underground tix at Heathrow (I didn't think there would be!) and the error message I was receiving was because I was on the rail website, not the Underground website?

the error message I was receiving was because I was on the rail website, not the Underground website?>>

exactly.

We're going to the Park Plaza County Hall hotel, and the hotel's website does provide detailed directions on how to get there:

And like most hotel websites it's written by someone who has never been within a thousand miles of the hotel and has all the soul of a dead aardvark.

For example it doesn't tell you that the change at Green Park is a nasty one if you follow the signs to Jubilee Line and ignores the jaw dropping viewing opportunities of taking the Tube to Westminster, leaving by the Bridge Street exit and walking across Westminster Bridge.

If you have more luggage than a small purse . . . the change at Green Park may kill you . . .

And yes, you can buy tube tickets at LHR. But a single ticket may or may not be what you want. You might want to buy an Oyster card - or not. Depending on if you plan on using any of the 2for1 Days Out discounts.

http://www.daysoutguide.co.uk/

It's wonderful to find such a fount of knowledge here. My mom and I will be each carrying a small backpack and dragging a wheeled luggage so the Green Park change will be out!

I do plan to buy an Oyster card for each of us, will probably just put a small amount on it at the start as I have printed out many coupons from daysoutguide.co.uk. As Waterloo Station is close by, we can pick up printed Travelcards for the particular days that we wish to use the coupons, and then Oyster cards the other days. We plan to return to London next year, so the Oyster cards will come in handy in the future...