There are a few alternatives to parking at the airport. Many towns have bus services to Stansted Airport and Taxis are another option.

The best option might be to get a friend or relative to drive you to the airport. You can always return the favour another time.

There are also companies that will collect your car from you at the airport and take it away to park elsewhere while you are away. They will bring your car back to the airport on your return. It costs a bit more but the convenience is probaly worth it.