....or if staying at Gatwick there is also the Sofitel. Nice rooms, a couple of restaurants in the hotel and easy access to the airport if you need to buy something.
Having said that, if I had rental car, or cost of taxi was not an issue, I would probably stay down in Brighton. Its only 20 min on the A23 and you're there. Brighton offers much better nightlife, restaurants and things to do to get your mind away from the training a bit. I have not been in Brighton for years but I know there is a Hilton down there as well, right on the seafront.
Possibly the best hotel in Crawley/Gatwick is the Arora, but Crawley is a dump. There are several small country hotels hidden in the leafy lanes of the area and as long as you have a car, that would be my choice and is what I usually do when in the area.
Otherwise, as others have said, Brighton. It has loads of interesting restaurants and a lot of variety, ranging from spectacularly bad tourist traps to very good. Quite pleasant to walk around, a couple of cinemas, lots of hookers if that floats your boat, a big gay population (ditto!), all in all it's probably the best choice.
Premier Inn just round the corner - the opposite end to the 'Candy Shop' - Porsche Dealeship!. However go to Brighton, Crawley and Burgess Hill for that matter are both dumps! (Apologies to those who reside there!)
Thistle Brighton, best choice of the lot, get a decent rate via CAE. Except for the scenes of devastation if you have an early sim session on Saturday or Sunday (yes, I've actually seen 14-year old girls dressed to shame a hooker sleeping in their own puddle of vomit..), the town offers a great choice of culinary and other diversions..
Hotel du Vin , a hundred meters on the left when you face the sea from the thistle (great restaurant and rooms although a bit expensive, ask Melissa from client services for negociated discount). Hotel Rooms in Brighton at Hotel du Vin
The Birch Hotel in Haywards Heath is closer than Brighton or Crawley - approx. 10 mins drive from Burgess Hill if you don't want to trek to/from Brighton. Its an OK place (a Best Western franchise hotel) but it isn't as cheap as premier inn style places.
Having said that, as others have said going to Brighton will give you a much better set of options - and Burgess Hill is only 5 mins from the A23 by car so Brighton is very accessible.
I'll join with PP and second Little Turrets if you want a change from hotel life.
Very aviation oriented guests in a purpose built new building and a private heli landing area just outside the patio doors no less. It's on a very quiet lane with houses less than 400 years old counted as new builds. I've stayed and liked it a lot.