T-Mobile in Europe

There are plenty of reports on T-Mobile. Whether the plans are new I do not know. Put "T-Mobile" in the search engine at the top of this page.

I just took my TMobile to Turkey, so I can't specifically address the countries you asked about. However, I was in some pretty remote areas of Turkey as we rode around on our bus and I ALWAYS had coverage. I had full coverage bars when we drove through tiny towns in the middle of nowhere, when we crossed the mountain passes to the coast and everywhere else. I was surprised. The one problem I did continuously encounter is that, when I tried to enable Wi-Fi calling so that I could place free calls, I had trouble connecting up. I was never able to figure out why. I just went ahead and did my calling at the 20 cents per minute rate and that was fine with me. Texting was free and I texted a lot and never had issues.

It sounds like you want to use it as a GPS. I have a Nokia lumina Microsoft phone that included "HERE", which is a navigation app. Here at home, I have downloaded my home state and it works just like a GPS. I put in where I want to go and I get a map of where I am going and a voice telling me when to turn, etc. It works without cell service or wifi, since it uses a satellite. When I went to France and England last September, I planned on using it just like I do at home. I downloaded the maps before I left...no problem, no charge. However, when I tried to activate the voice, it said I needed to pay $19.95 to use the app internationally. I did not want to do that, so I just used the map feature to watch for upcoming turns, etc. I did have to know where I was going and have some directions, but the phone was very helpful in knowing when the turns were coming. It always worked, even when we had no cell service because of working off the satellite. Most importantly, we were never charged anything from T-mobile. (the plan does just what is says...free texting, free roaming and downloads, 20 cents a minute for calls.) I am no expert on this stuff, but that is my experience. I would probably take my Garmin if I wanted to be sure I had a GPS.

The HERE maps from Nokia that can be used "offline" are now also available for Android devices in the Android app store.

I posted about my experience here and several others added comments about their experience:

https://community.ricksteves.com/travel-forum/tech-tips/my-experience-using-t-mobile-s-simple-choice-plan-in-6-european-countries

I used T-Mobile last year throughout Spain and Portugal without a hitch. I just came back from France and used a Lebara SIM card which cost me 27.50€ for two weeks (7.50 initial cost + 20 top up). TM cost me about $45 and seemed to work seamlessly and a bit better than Lebara. Also, if folks in the US wanted to call, they'd just dial your US number. I didn't have to take my GPS, just the phone.