I fly the RJ100 into Jersey fairly frequently,our departure profile is such that we accelerate at 1000ft. above the airfield and make none of our turns below 1800ft. so as mentioned above it depends on variables such as a/c weight and ground speed(determined by the wind on the day) as to where exactly over the land we will be when flaps are retracted from 18 to 0.
It is also worth mentioning that we can do a number of different departures, all of which will vary our routing out over the island.
Hope this helps.