Route planning

Hi all.

I'm relatively new to trying to fly a quad that's able to go more than a thirty seconds walk from where I'm standing - the biggest thing I'd flown until recently was a Sympathetic X5C (which is just about okay in a moderate wind), but I now have a Mavic.

I'm thinking to go for a fly near my sister's house, since she's in rural Wales and I'm almost under the London exclusion zone. For cost, safety and not littering reasons, I'd like to plan a flight so if I have a failure, I can always retrieve it - which may not be trivial in very hilly areas. I mostly trust everything to be solid, but a Mavic doesn't have the redundancy of a commercial octorotor, and if I somehow have a prop fall off I'd rather play it safe.

Other than staring closely at Google earth, does anyone have good suggestions of how to route plan conservatively?