Andrewsfield is a good one and a half to two hours drive from London (on a good day).
Stapleford, is good.
Not sure if there are any airplane to rent there but Thurrock is pretty good for London; you would need a car or will be spending a lot on Ubers from the railway station.
On the basis of travel time to get there Southend would be an option - out from Fenchurch Street with the student rail card.