womba
4
Since posting this question I have done some further research. The following links are relevant:
https://forum.cyclinguk.org/viewtopic.php?t=127532
http://www.bicycles.net.au/forums/viewtopic.php?t=93718
Komoot
https://blog.komoot.com/how-to-navigate-any-route-on-komoot/11475
KML / GPX etc. file formats are interchangeable as there are free conversion programs available. The RidewithGPS app will do the job apparently but probably at significant cost although there is some uncertainty in the threads above about what can be obtained from a free version.
The Komoot app seems to offer the best solution. The first map for offline use is free and that seems to be a very reasonable approach to cost. When the app was first opened it seemed that nothing was available in my area and I would have to pay for a map. So I put the app aside. When I next looked at the app it had mysteriously acquired the map for the Perth area.
If Komoot is given a Perth start and destination for a cycling route it only offers a road solution. But I was able to import a GPX file of a cycling route exported from Google Maps which used cycle paths through parks for the same start and end points. Komoot only accepted this as a hiking route but did offer turn by turn directions based on the imported file.