I wonder if the recent declines at the Hilton Gatwick are an echo of the declines at the airport as a while. Besides the whole global recession thing, Gatwick seems to have lost all of its high paying London to US Market on carriers that didn't have slots at LHR. Since the business travelers (to the USA) are all at LHR now, why spend money on Gatwick or the Gatwick Hilton?
The Hilton Gatwick is in the middle of a major lobby and restaurant renovation and remodelling program. They have just completed a refit of the entire TV system and prior to that an entire bathroom remodelling. When you have 800+ rooms and 90% occupancy, these are very challenging programs to manage. I know the GM quite well and while business is definitely down as far as yields go, the Hilton's location alone ensures that they can maintain occupancy rates no matter how sour the economy goes.
FWIW, the plurality of the Hilton's clientele are not business customers but rather package tourists using the hotel as part of Park N' Fly packages or as a stopover at the start/end of their vacations. There is also significant business from delayed/cancelled flights and also airline crews.
The hotel continues to deliver a high standard of service and most importantly, are receptive to any complaints received, no matter how minor. With over 300 nights spent there in the last 5 years, I've gotten to know most of the long term staff very well and quite honestly, there is nowhere else I would consider staying when in the Gatwick area.