Having spoken to the BAE UAV project team 3 years ago they were looking to compliment Air Support rather than replace it. They were keen to find out which tasks were more suited to UAVs, ie the longer term/planned/repetitive/hovering over one point or flying a preplanned search type job, as opposed to the aerial detective agency/fast paced/changing perameters type jobs that are the domain of manned aircraft.
As I say, this was 3 years ago and the country and the economy have changed a lot since then! The opinion then was that these UAVs would save operational helicopter hours and thus reduce costs (slightly). The larger types still require significant infrastructure such as ground crew operators working shifts, vehicles, an airfield or short strip to operate to and from, fuel installation, maintenance etc, infact not unlike an air support unit!