Stand planning is a function of the airport authority and they would normally plan to allocate 'normal' stands in the plan..
There are two stand planning operators at Gatwick. The airport owners, and British Airways. BA have an apportionment of stands in the North Terminal which they allocate to BA and SZ flights. Gatwick Airport allocate all other stands. Generally airlines have preferred stands, but there are few if any guarantees that any particular flight will always operate from the same stand. Stands are a precious resource, and are worked very hard during the peak hours.
South Terminal operators would not normally be allocated a parking stand on a North Terminal pier. Obviously the remote stands are available for use by any operator regardless of terminal. The major exception is easyJet, which has a dual terminal operation, so depending on aeroplane rotation may have a South terminal flight arrive on a North stand, if the departure flight is from the North terminal.