The circle line tube takes you straight to Paddington (so does the 205 bus if you'll consider buses).
However, just wondering why you're taking the Heathrow Express as the Piccadilly Line tube goes straight from King's Cross to Heathrow, will only take you about 15 mins longer overall, and is far, far cheaper.Edited: 8:50 am, December 10, 2011
20 minutes on the tube, taxi will be pushed to beat that.
Take any Westbound Circle or Hammersmith & City line train. If you have a lot of luggage, Circle is best as there are fewer or even no stairs if you take the lift just on the left of the magazine shop once you come through the barriers. Otehrwise there is just a short flight of stairs or a short escalator.
EDIT: and lava_tory makes a great point, once you factor in waiting time for a HEX, tube will be pretty much the same time and save you about £20.Edited: 8:54 am, December 10, 2011
Tube. Kings Cross St Pancras on Circle or Hammersmith & City Line direct in less than 15 minutes.
Allow a bit of extra time for congestion at Paddington though as the Undrground station is being rebuilt and it is rather cramped at the moment. The good news is that a new station entrance and new stairways and lifts will be opening early in 2012.
Also, if travelling at the weekend or between Christmas and New Year, check for scheduled engineering closures.
If you were to get the tube to Paddington, I would just get the tube (Piccadilly line) direct to LHR.(£5 single*)
Otherwise taxi to Paddington will take around 20 minutes and be about £12-16 plus cost of HEX or HEC.
*Tube fares go up slightly in Jan 2012.Edited: 9:00 am, December 10, 2011
Thank you all! Tube direct to LHR sounds like the best plan, thank you!!!
I was in this situation once and my cab fare from that area to Paddington on a Saturday morning with little traffic was about 5 pounds. At the time, I had a prepaid ticket for the HEX which is why I didn't take the tube direct to LHR.
Hi and thanks again.
Having completed this trip I will report that I left my hotel, the Renaissance St. Pancras, at 9:15 and saw heavy traffic, so I walked the 100 yards to the tube, waited in line for five minutes to buy a ticket, walked down to Platform 1 and waited three minutes for the Hammersmith Line, arrived at Paddington Station at 9:40. I bought my HEX ticket and missed the train by 1 minute and boarded the 9:55. We left on time and I arrived at Heathrow Central at 10:10, got out and waited for the connection to Termina 4 for about five minutes, and arrived at Terminal 4 at 10:20. Very easy and smooth.
Thanks for your help!
So, you decided against the cheaper, no changes route of just taking the Piccadilly line all way?
Yes, I wasn't interested in standing on a crowded tube for 75 minutes at rush hour. Besides, when you sit on an airplane for 8 hours, getting some exercise in the morning is nice. Obviously, some may prefer the tube, but this worked out well for me.
You wouldn't have been standing in a crowded Tube train for the whole journey to Heathrow, only for the first few stops. People are travelling into central London at that time of day, not in the other direction.