Being an F.I. is hard work for little monetary reward. In the summer you will work every hour god sends and then sit on your back side in the winter. Sure on a good day in the summer you may fly 4/5 hours at £40 p/h but during the winter months you will be lucky to fly 10 hours a week and a FI week is seven days.
You cannot bank your chances on earning £2000 per month (take home) as an FI. Never. If you do you may become dissapointed.
As whats been said the N.Sea route is by far the best route to earning some decent money but the IR will set you back £30k upwards.
Good Luck.