Delboy, your only 40 mins drive from the airport.
personally, if I were you, I would consider getting a taxi as there are many of the airport parking companies that just dump your car in a side stree around the town somewhere.
Places like the hotels (Check the Gatwick Manor Premiere Inn) let you park the car and come back a week or two later. Others need your keys so they can shuffle the cars around if needed. Purple Parking is about the only one I can work out where you take your car in and it stays within their compound.
I live near the airport but don't do airport parking :Pokefun
I have an early flight in a weeks time but I will just get a cab there and leave the car tucked up at home.