Watchkeeper, about the size of a Cessna 150 is to fly in the following area:
Population of Salisbury is ~40,000 and the population of Wiltshire is ~460,000. So what is your definition of "congested area"...
Accident rates for Predator are better than that for single engined GA aircraft in the UK per 10,000 flying hours - so define "safe"...
Lots of US presentations online - see slide 7 for a GA comparison here:
http://www.asma.org/asma2010_mp/pdfs...resent_018.pdf