NB - Just because a flight leaves controlled airspace, it doesn't mean that you must fly VFR and that it isn't possible to continue flying IFR. It happens every day in the UK. The increased risk of coming gnats-whisker close to other aircraft outside Class A is usually a key factor that companies don't like.
To be able to fly VFR only through areas such as military airspace, is done for a very good reason. We all know company pressures can, on occasion, lead to cutting corners. I make sure that I don't fly with operators who allow the (passenger-paying and unaware) white-knuckle ride through the middle half a dozen fighters carrying out vis-idents or simulated combat intercepts!