Contact the BAA at Gatwick, or perhaps the local council that Gatwick falls under, and they should be able to provide you with a map similar to this one for Heathrow showing the tracks taken by landing aircraft.
An average day at Gatwick would have a few straight in approaches and so they should show up on the map.
From the BAA website, try Aircraft Noise Tel 0800 393 070 (UK only)
[email protected] as a first point of contact.
WF.
