You're welcome! We're all still learning. Thanks for the reply and for taking the suggestion onboard. Regarding the question of showing they're the same unit, I'm not totally sure. If I'm not totally sure how best to map something, I sometimes try to find other local (or not so local), similar examples and see how they've been mapped. 
This ( https://community.openstreetmap.org/t/public-access-defibrilators-emergency-defibrillator/112371 ), in the section about booths may help, but it's talking specifically about disused telephone booths rather than active ones. It's quite possible you can combine tags and make them one object, but I'm no expert.
Actually, I've just found one local example, here: https://www.openstreetmap.org/node/1985840345#map=19/52.052109/1.153915&layers=N which has both emergency=defibrillator and amenity=telephone . 
Also, if you run this query on Overpass Turbo, you can find more examples (just move around the map and press the 'Run' button to find more examples of features with those two tags to see how they've been mapped. Hope this helps! :-)