Term 4 Heathrow via tube Picadilly line.
 

What is the procedure to downtown London via the Picadilly line from Terminal 4? It has been a year since last trip to London. Am going again in December 2005. It is the way I will go.

The T4 tube station is closed for another year (while the line is being extended to T5). You'll need to take the (free) shuttle to the Hatton Cross station. Haven't done it; assume it's a hassle with bags.

While of course it would be better to be able to simply hop on the tube without a bus, at terminals 1,2,3 there is a rather long walk to have to take your bags. At T4, you simply get on the bus right outside and they leave you just outside Hatton Cross station....if you can schlep your bags onto the tube, you will be able to get your bags onto the bus...it's not the end of the world.

You can also take the Heathrow Express (it's free from T4 to T1-2-3).

And don't forget to watch http://tfl.gov.uk/tfl/planned-works for notices affecting service (because sometimes they work to your advantage).

This weekend, for example, a Zone 1-6 Travelcard is good for a ride on the Heathrow Express between Paddington and the airport.