Convenient, cheap and directly approached from the heart of London. Though be aware that the tube ride takes much longer than you may think. Approximately 1 hour.
Star Alliance Gold members riding Heathrow Express can upgrade to Business First for free. Just buy a regular ticket, take a seat in the car, and show your Star Gold card to the inspector
Don’t pay for Uber when you can roll your wheelie bag right onto the train. Elizabeth Lone takes you to Abbey Wood for about $20 USD versus $100 taxi ride.