iPhone GPS use in UK and Portugal- best data plan for travel?

We use Verizon on international travel including Europe on my husbands iphone. We get the $70 per month plan that includes texts. If you have any incident abroad or at home it is a life saver.
I get a local SIM card for my iPhone and use that for GOS. We leave our Garmin with Europe maps home now, less to pack.

We will be in Portugal for a little under 2 weeks and in the UK for 5 days. data ? I have never gotten a SIM card in several trips to Europe and I have no idea why using one seems so confusing. With a non U.S. sim card how does Verizon still work? OOPs, apparently we have AT&T. I used to have verizon but no more.

Thanks so much, CS

None.

You don't need data at the time you are using GPS. As long as you download the maps you need in advance at a time you have data (at home or on a hotel etc. WiFi), you can use maps and GPS to plot and display routes without any data connection.

I did this last week. Plotted a route from Vienna to Zürich while sitting in my hotel room. It downloaded a chunk of maps. During the trip, without data, I could follow the route on my phone.

"Will a SIM card purchased in Portugal work in the UK?" -Yes, however it will retain its Portuguese phone number. At least it will as long as the UK remains in the EU, after that it is "TBA, all questions to T May, 10 Downing Street".

I have used "Maps.Me" on both IOS and Android devices in data-less environments and it works about as well as dedicated GPS device. Just download ALL the maps you need beforehand (while you're on WIFI).