Thanks for the reply Mads.
It does go towards solving part of the problem.
When adjusted in Resolve, the colour is improved a bit, but it still looks incorrect, like the gamma is skewed somehow. It feels like my Mac may need a plug in or something to make sense of the IPhone footage. Also the exported clips from Resolve are absolutely huge, 500gig + as opposed to a couiple of gigs when they went in.
Many thanks,
Dan