We like to stay at the Sofitel too, as nemmie says it's usually around £100 a night but I think it's worth every penny for the location. If you sign up for ABC Holiday Extras emails they'll probably start sending you links with booking discounts ie 5% although if you book through Quidco you'll get cashback.
Each time we have been to Gatwick, we have stayed here, and never been disappointed - http://www.springwoodguesthouse.co.uk/ - It is very close to both terminals
We've booked for the Premier Inn Gatwick South in Crawley for the 2nd time. For a double room, including buffet breakfast its £85 for September time, one night stay.
The beds were reaaaaaaaally comfortable, and huge, had a lovely deep bath and it was very very quiet.
The neighbouring Gatwick Manor Pub serves delicious food for dinner and the Premier Inn breakfast. Delicious.
All in all, not a single complaint whatsoever about the Premier Inn Gatwick South
we always stay at the sofitel too , love it there, but we book park and stay doesnt work out much more than parking alone, and best bit walk through the tunnel and car is there waiting for you on day you return, much better than the car parks bus thing.
I love the Gatwick Hilton too, have stayed their numerous times and have always had a great stay. Its only a 5 min walk to the terminal so you have a great choice of places to eat/drink in the evening too.
You can get a great deal at the moment if is a weekend day as they have 50% off. They have other sales periodically too.
Its worth becoming a member of the hilton honors scheme too - you can earn points and virgin miles for every stay. Plus it means you get to go to a seperate check in desk which is usually a lot quicker . I think if you get someone to recommend it to you, you get a welcome bonus too - or you used too when i joined anyway.
We always stay at Acorn Lodge B&B - parking, room, breakfast and transfers usually come in at not much over £100. Its clean, and they are always really punctual picking us up after our flight.
Can't remember the price, sorry, but we have stayed at the Travellodge which included parking offsite at Gatwick and it was about £10 more than the cost of the same parking alone, this was for October