If you arrive at London St Pancras train station on the Eurostar and need to transfer to Heathrow Airport, you have several options. They are compared below.
London Underground from the Eurostar to Heathrow Airport
From the Eurostar, you can transfer to the London Underground (tube) in St Pancras Station. Take the Piccadilly line all the way from St Pancras to Heathrow Airport. The trip will take 55 minutes to an hour if there are no delays. Make sure to leave yourself time, though, as delays are common on the tube.
Taking the Underground is the cheapest way to get from the Eurostar to Heathrow Airport. Fares vary depending on whether you travel at peak or off peak times, but ticket prices are around £5 if you get an Oyster Card at the station.
Trains from the Eurostar to Heathrow Airport
Alternatively, you can take a combination of the London Underground and a train from the Eurostar to Heathrow Airport.
First take the London Underground’s Circle or Hammersmith & City line from St Pancras train station to Paddington station. This will take around 10 minutes and cost £2 if you get an Oyster Card at the station.
From Paddington Station there are trains to Heathrow Airport. You can either take the Heathrow Connect, which takes around 22 minutes to get to Heathrow from central London, or the Heathrow Express, which takes 15 minutes to get from central London to Heathrow Airport.
Heathrow Connect tickets cost £9.10 for a single, and Heathrow Express tickets cost £18.00 for a single in standard class and £26.00 in first class if you purchase tickets online. Otherwise they are slightly more expensive.