Originally Posted by EMA ON BA

A few alternative alternative options avoiding the Jubilee line are -

London City - (DLR) - Bank - (Central Line) - Lancaster Gate - (Walk) - Paddington - (HEX) - Heathrow T5 or DLR to Stratford for Central line to avoid Bank and get on at the start of the tube trip

Plugging in a 7:45 departure time from London City Airport suggests a 9:16 arrival time at Heathrow. I almost always travel to Paddington using Lancaster Gate station and the walk takes around 10 minutes with luggage.
Pros - Fewer changes, you may be able to get a seat on the DLR. DLR and Central Line tend to be among the more reliable public transport options.
Cons - Changing at Bank with luggage, particularly at rush hour can be a pain.

London City - (DLR) - West Ham - (Hammersmith & City Line) - Paddington - (HEX) - Heathrow T5

Plugging in a 7:45 departure time from London City Airport suggests the same 9:16 arrival time at Heathrow.
Pros - Fewer changes, DLR likely to be less busy on this line in this direction. Newer more spacious tube trains on Hammersmith & City Line.
Cons - Hammersmith & City trains are less frequent and less reliable than Central line (longer delays etc.)


London City - (DLR) - Woolwich Arsenal - (Southeastern mainline train) - Charing Cross - (Taxi) - Paddington - (HEX) - Heathrow T5

or WA to Cannon Street then circle line to Paddington or district line to Hammersmith or Barons Court then across the platform to the Picadilly line to LHR

A 7:43 departure time from London City Airport would get you into Charing Cross for 8:28. Allowing 40 minutes for the taxi you would get to Heathrow at 9:31. With lighter traffic you may make the same HEX train as the options above and arrive at 9:16.
Pros - Avoids the tube, decent chance of a seat the whole way to Charing Cross. Easy change at Woolwich Arsenal (short distance but does have steps) [there is an over pass from the DLR to rain platform level with a lift
Cons - Southeastern trains can be delayed by congestion at London Bridge. Most expensive option.