Why does Reaper need to fly in UK/Europe? You fly it in theatre and once the war/conflict is over you put them in a box and wait for the next one. For OCU and LRE/crew currency base/detach/borrow one or two in the US and do the rest on simulators. In peacetime they will be the cheapest Sqns by far to keep current and capable until needed with no airfield requirements (ATC, crash CAT, Med cover, etc. The Sqn doesn't even need to be at an airfield, but it is useful for direct C-17 access), virtually no fuel bill, reduced fatigue and maintenance, no noise complaints or pollution, etc. They are not like other types that need dragging out the hangar every morning for a couple of flights and intense use in work ups for deployments including expensive transits/deployments to the US and very poor FE@R ratios in comparison. I'm not saying I like drones but that is the reality, they will provide excellent bang for buck!
If Euro Hawk was going to operate at FL700 ish, why couldn't they just have had a bit of restricted airspace for the climb/descent, there isn't much up there to bump into? With significant endurance and good planning to avoid busy periods they would only need to close a bit of airspace for a short period once a day perhaps?