Hi stuart1974,
If I may intervene during your discussion. I experienced, there is less than two years, a very powerful UVA. This is the Gatewing x100.
I could test it in a very extreme conditions and it is behaving in a good way.
It's effective combined with Agisoft PhotoScan, and you get a good visual outcome. Maybe Pix4D Mapper is more than efficient, but I do not had the time to test it.
darksabersan.