I use the OS Maps app on iPhone/ipad. Don't use it for directions, just figuring out where I am/want to be. OS mapping is free if you have a data connection, and you can download maps you've paid for on paper onto the app for offline viewing.
I use OS maps loaded on an sd card in a garmin
I got the whole of Britain plus the Swiss and French alps for about £25
Try ' talkytoaster' he's very helpful. Will do any custom package you choose. Can send a file for self load . Or will supply a card preloaded to pop in a device.
Maps are very detailed .
Great product and service
Try looking at AllTrails app. I’ve been using it in a late model iPhone in a Quad Lock case. The app is meant for all categories of trails from hiking to mountain biking with filters for search. I’m in the US but I checked and there seems to be many entries in Europe & UK & others. Free to use, but if you want to download the trail map to allow you to follow your trail without cell signal (using the GPS on the phone) you have to pay a small/reasonable yearly charge.
Let me know your comments and trail availability outside of the US.
I tried the free version of Cyclemeter , it’s like being in google earth . All dependant on batteries and mobile phones and learning how to use the software which Iam not very good at So I just use a map generally or the map on ViewRanger
I used Komoot recently with turn-by-turn navigation and it took me down some interesting off-road bridleways. Worked fine with quadlock mount but apps do quickly eat into the phone battery. Best to carry a USB charger packed near mount. Or consider a Wahoo or Garmin to save your phone from the hard knocks!