Copied the .mp4 files from the SD card to my RAID drive and firstly tried to open in Resolve 12. It didn't recognise the footage so it would appear it needs transcoding before bringing it into Resolve which is a shame. Not a problem though.
So tried Premiere. No problems editing native files. Full 4K on the timeline. Tiny bit glitchy when I added a time reverse effect but nothing a render wouldn't sort out. Footage looked okay with no colour correction at all. Pleased! Exported full 4K at ProRes HQ. Converted to iPhone friendly version using Soreson Squeeze. Uploaded file to DropBox. Then saved to iPhone from DropBox and shared on WhatsApp and Instagram. Seems easy enough.
With the next test I will convert the native footage using Squeeze to ProRes and see if Resolve can handle it. I would like to learn Resolve after all.