" ...base maps supplied in handheld units such utter rubbish?"
It's a common moan on Amazon, but Garmin don't know what mapping users need: hiking, topo, nautical, street mapping or aeronautical, nor do they know which country they want maps for. Hence the base map.
The in-car Garmin units come with City Navigator street level mapping. That's available for the Etrex series on an SD card at reasonable prices and you can swap it between units. It contains much more data; hotels, gas stations, restaurants etc and is updated annually. (City Navigator Europe 2014 is available and works with the Etrex series)
Free routable contour maps for the UK are available from Talkytoaster as you point out, (do leave a donation) and for the rest of the world from garmin.openstreetmap.nl. They are good enough for driving through Bulgaria, as this Etrex user has just done.
One point which most of the reviewers miss is that the Etrex 20/30 receivers have Usage Profiles, and can also store and display more than one map. So it's possible to set up a profile for say Driving with 3D views and nav-prompts, and set it to use City Navigator, and also have another profile called, say, Hiking, and set that to use Openstreetmap contour mapping. I have a third profile called Europe which switches the Units to Kph, and loads Romania and Bulgaria road maps.
If you use Basecamp, the free Garmin PC software, City Navigator and also Openstreetmap from the Etrex can be displayed on screen and waypoints and routes created then transferred to the Etrex.
It's also possible to scan and create personal maps for these units, so the range of free mapping available for the Etrex20/30 is very large indeed. The basemap is only there as a backdrop for waypoints.
I agree that these units are much better than the previous Vista series.