Turn by turn

Turn by turn should be on by default.

The setting is under

Navigation -> Courses -> 3 dot menu in top right hand corner. 

Check that the maps for your area are installed and active.

Activity profile -> profile name -> navigation -> map -> map information 

Thanks! That may be the problem. When I go to the map information screen it shows no information there as shown in screenshot. Should I do something to enable the maps?

I guess I should say that the maps have worked fine in my local area of Hampshire and on a weekend trip to Cumbria too. I hope they'll be fine in the Alps next week. 

Use Garmin Express on a PC. It should offer you an option to manage the maps. You may have unit meant for a different region. If so you may have to uninstall those maps and install the maps for your area.

Thank you. I’ll give that a go tomorrow. I’ll be cross if that’s the case.  I just bought it from Wiggle. 

What region are you in?

The 540 has two different EU models with different combinations of the 3 EU maps as only 2 of 3 will fit on the unit.

Wahay - you may have cracked it! I've just synced on Garmin Express, updated the maps and now I have an option to toggle the Turn Guidance (which was completely absent before). I'll take it out later and see it it now works. Thanks for your help. (and I'm in Hampshire, UK, Europe, by the way).