Long layover at Gatwick?

You have a few hours, say 9:30 to 12:00 at latest. There is a smallish town a few minutes away. You could taxi there, walk around and have breakfast or lunch, then head back to Gatwick. I forget the name of the town; it has a high street, a train station, a couple of larger stores, residential streets and a couple of places to eat. As I recall, Gatwick has some businesses, but there's not a lot to do there.

I've been told Brighton is lovely, the train is about a 30 minute ride. Worth it to go for a couple of hours?

Unless you have made a typo, 9 to 4 is c 7 hours not 8.

It will take you an hour to get off the plane and through immigration (note Customs is just a walk through unless you have something to declare, it's queuing at immigration that takes the time). Unless you want to carry your bags around with you, you will have to put your bags into left luggage. So you maybe ready to leave the airport at say 10.30 earliest, if your flight is on time.

For international flights to the States, the recommendation is to be at the airport 3 hours before departure, so you will need to be back at say 13.20.

That leaves you under 3 hours. It will take you an hour to get into central London and an hour back, so IMO not worth the risk of a transport delay or the cost for such a short visit.

Crawley or Redhill are nearby towns, although not very inspiring, it will give you the opportunity to stretch your legs and grab some lunch - trains leave Gatwick every 10 minutes and only take 8 minutes each way. Trains to Brighton on the coast are also regular and take 25 - 40 minutes depending on which train you catch. Brighton is more interesting than Crawley or Redhill, but if there happens to be a problem with the train line, it's easier and cheaper to get a cab back to Gatwick from Crawley or Redhill.

Yep, math fail right there. We will have already gone to London so that won't be of interest, looking for something different. Being in an airport that long is no fun at all, but I suppose if I'm forced to I can make do. Thanks for the note, I'll check out those towns. Anything is better than an airport.

We found ourselves in the same place in April, 2016--waiting for a flight to Rome.

It was just not quite long enough to go into London and the express train into the city is quite expensive.

We just sucked it up and waited in the mall area upstairs taking short naps.

I would note that Southern Railway that serves Gatwick has not been running well lately so going to any place served by them is questionable. On top of the day to day delays and cancellations they have several strikes coming up as well. If you go to Brighton, I would take Thameslink.

If you found a decently priced limo service to take you, you could go to Hever Castle, just outside of Edenbridge, to the east of Gatwick. Hever Castle is a manor house, the home of Anne Boleyn, second wife of Henry the 8th. Your limo would have to wait while you toured the house, then whisk you back to the airport.
http://www.hevercastle.co.uk/
I don't know if you have time to do this.
A rushed version of this would take about 2 1/2 hours.

Thanks all, while we did have plenty of time yesterday to go outside the airport we opted on a well spent 49 pounds at Yotel for 5hours! Highly recommend for relaxing. Got some extra sleep and a shower right in the terminal.