Rob, just re reading your post here.
I am pretty sure if you have the Hema 4wd app, You can download Memory Maps and use the maps you already have plus buy or import others.. Better still you shoudl be able to do the same with Memory Maps for all. This has so much flexibility in the screen layout and functions. If you use the same account login as your Hema 4wd app then it should all be there for use.
I have already asked that question and it is a no go, you have to start again with a new license
“If you bought maps using Apple "In-App" purchasing within the old Memory-Map or in the Hema app, these are unfortunately not usable in Memory-Map for All. Apple's rules require the purchase to be used only within the app in which you made the purchase.”
Did I just restore some tech cred?