I'd bet my last dime that the boys at Spadeadam would have a pretty easy time jamming most UAV's, even the sophisticated ones like Global Hawk.
Their "interference" would be enough both to upset the UAV's mission (stop the flow of data back to the ground rx) and possibly to disrupt receipt of its autopilot/command systems dealing with navigation/control either enough to cause it to crash, or to deviate off its intended course.
What's the survivability of a UAV compared to a manned (womanned) ac in say a Red Flag environment?
MB