From other posts it seems there is a limit of 50Mb for Data storage on mobile Safari (IOS 10)
Example SO post on Limits
Questions about achieving more under ios7 remain unanswered.
Is there a way to store more tha 50 Mb with a HTML5/Javascript app on mobile safari?
or are we forced to look at Cordova style solutions ?
Is there a non Native app solution ?
EDIT: We ended up building a Hybrid App.
RANT: In my view Apple is deliberately sabotaging SAFARI so people have to build native apps so Apple can take a % of sales. If people can build good HTML5 apps then there is no need for a store APP and Apple is just a platform. Greed will come back to bite you Apple.