I learned to fly at Stapleford many years ago.
I didn't realise the Wright Brothers had the franchise there!
How do you get to Stapleford by public transport? Its bad enough by car.
Southend is a long way out of London, but the train runs alongside the airfield. Buses run from Rochford and Southend stations and the trains are regular and quite quick. There are also 3-4 flight schools on the airfield too.
Earls Colne is is a similar situation, I think Kelvedon would be the nearest rail station.
Trains to both Southend & Earls Colne leave from Liverpool Street, rumour has it that a train station is to be built at Southend Aiport, but I first heard that 40 years ago & its still not happened.