This is a useful reference site:
IVAO United Kingdom - Gatwick (EGKK)Helicopter Operations
For helicopters wishing to transit the field, 2 VRP's have been established for this purpose. They are the Airport North Terminal and the British Airways Maintenance Area. Helicopters should be given a Gatwick squawk, given a VFR clearance to the appropriate VRP and asked to report Gatwick in sight. Once the helicopter reports the field in sight, they should be passed to AIR for crossing. They will then be told to hold at the next VRP and contact INT for further. Helicopters wishing to land at Gatwick should be treated as crossers and will land on the main runway (There is no dedicated helicopter landing area). Departing helicopters will be treated as fixed wing departures.