You really cant go wrong with view ranger, been using for a couple of years now. The free maps do provide a good compliment to use when planning and satellite view is good for seeing those paths not shown or gaps in walls.
If you are a subscriber to trail magazine you get a full free year access to OS maps although think it is going to half price soon.
I make all my routes on the app and then transfer to my map. Taking an android device with the app on gives a good second backup and if you have android the recording part even works in flight mode, so great for battery life.
Just make sure you sync device before going and download map to device in case the signal disappears.
Have fun and join the 2019 challenge