Having just spent 1 Hour 45 mins on a Stansted / Liverpool street train
, I must echo the need for alternatives. I suggest:
Plan C
Taxi: STN Taxis are provided by Airport Cars Tel: +44 (01279) 662 444. Hiring a cab is expensive (GBP 100++) . I also think they do a shuttle service between to Heathrow & Gatwick which is cheaper. It might be worth giving them a call.
Plan D
One way hire of a group A car. One of the hire company's (It might be Avis, but don't bank on it) does not penalise you for doing a one way hire. By road it is motorway all the way M11, M25, M23. It is 74 miles and the AA reckon it should take 1 Hr 20 mins. You also need GBP 1.10 for the dartford crossing toll.
With Apologies!
"If you want to get to Gatwick, I wouldn't start from Stansted"
Good Luck
EG