"This is my first test of the Grammarly app which is as it turns out is really good and got most things that I misspelt completely correct so I will give this a try for a while as my typing on my iPhone is quite often dreadful!"
You can download this from the Apple App Store
Apparently it works in all Apps but does not support external keyboards so I can’t use it on my iPad Pro (yet).
I typed this out quickly in an email and it only missed one typo picking up and sorting the rest very impressively.
I will continue to use Grammarly on my iPhone 7 Plus and report back in the future.