While I generally applaud their plan to try something new, I wonder why this is more feasible than say, using high-resolution satellite imagery? At 30 cm pixel resolution, it's certainly possible to see the hedges that demarcate the property lines.
A possible advantage I could see is if the area is notoriously cloudy, a UAV will be able to fly below most of that cloud cover.
As a commercial UAV operator myself, I also suspect they will receive resistance from certain landowners whose land they are flying over, where the satellite route removes a lot of this friction.
Awesome, would be fun to do that in the U.S. as well.