In reply to John Workman:
I use an Ulefone Armor5, which was recommended to me by some folks on another outdoor instructors site. It is Chinese, and therefore pretty cheap, but is bulletproof so far, which is well over a year, used daily and pretty much abused, both in the UK and abroad.
It has a really chunky 5000ma battery, and alongside my Memory Map app as well as Viewranger when in Russia and Nepal, worked great.
My only niggle is the camera is poor in low light, and that's it - It's excellent in good light.
£130 plus £14/month SIM only. Bargain. I will have another if they upgrade the phone.