Seems like an odd story - according to the Guardian (6th May) the UK military already owns around 500 UAVs, so why get hot under the collar when US-owned drones overfly the UK on specific, agreed and non-covert flights?
US-owned military assets already fly daily in UK civil and military airspace, so requesting overflight facilities for effectively just another highly capable aircraft doesn't seem like much of a step. US fast jet and other aircraft currently based in the UK have camera systems every bit as refined (and probably more refined) as those fitted to drones.
UK-owned military drones have normal access to UK military airspace, and apparently some limited civil airspace, and it appears likely that they will be able to access more civil airspace as time goes by. Flown by military operators in military airspace at present, movements do not have to be accounted for.
UK police forces have experimented with drones since around 2008, and several forces own them - but it isn't clear how much they actually use them.
If anyone wants to worry about any aspect of drone operation, I'd suggest that the increasing availability of radio controlled camera-equipped drones of various sophistication to members of the general public is a much more concerning subject. You can presently buy a drone able to legally operate up to 500metres away from you, and up to 122 metres high, over the counter at Maplins for a few hundred quid, and much more capable vehicles from online sources at rather higher prices!
