My Canadian cell phone in Wales

Look into using an eSIM (virtual not physical); it will save you a ton of money. Your iPhone 15 will support one as long as your service provider has not locked the feature. To check, go to SETTINGS….GENERAL. Select ABOUT then scroll down till you see ”Carrier Lock”. If it says “No SIM restrictions” you can add an eSIM.

We’ve used Airalo (data only) eSIMs twice now when traveling to Europe (there are other companies that offer eSIM too). The Airalo’s webpage has info on what an eSIM is and how it works.

https://www.airalo.com/help/about-airalo/NFHQSUXFCZOM/what-is-an-esim/58HW9139AYWB

And this is a good video to watch:
https://youtu.be/CujQmwCK3dE?si=tbg__Ag6KUR0JFS2

These are the notes I made when we used Airalo in August (so I’d remember for next time). It was easy to set up. Once set up, any Apps that use data work via the eSIM’s data (not your hime carrier’s setup). We used WHATSAPP (Wi-Fi based) for texting and calls.

1. From the App Store download WhatsApp. Download Airalo app; purchase an eSim in the app before leaving home. Wait till in Europe to set it up.
2. Turn off cellular data for all apps.
3. Place phone into Airplane Mode when boarded airplane
4. When arrive/land KEEP PHONE IN AIRPLANE MODE
5. Once in terminal connect to WI-FI  
6. Open Airalo app and select to set up the eSim you purchased - just follow their instructions
7. Finally go to Settings - Cellular to finish set up…. label eSim TRAVEL, select data roaming and turn on data for apps you plan to use (WhatsApp,maps, safari, wallet, etc)

Even with an eSim installed for data, if you want to ensure you don’t inadvertently incur charges from your cellular service provider (especially for unexpected SMS messages sent to you or background app updates) do the following:
Under Settings > Cellular
1. Turn off WIFI Assist (so your phone doesn’t automatically switch to cellular data if WIFI is slow)
2. Toggle off “use of cellular data” for each app listed.
3. Turn off Background Refresh for all apps
Under Settings > General > Background Refresh select “Disable”
4. Disable SMS messages (SMS are sent using voice stream)
Under Settings > Messages
Toggle/Disable “Send as SMS”

There is also a nice Monday Night Travel presentation on using your phone in Europe that might help answer some questions on phone use
Traveling Smartly with a Smart Phone with Gabe Gunnink
https://www.ricksteves.com/travel-tips/travel-classes/monday-night-travel/smartphone-travel-skills

Thanks so much for all of that info .! I’ll viewthe video first .

I agree. I travelled to Wales in November and used an esim from three. Paid for it and set it up the day of my flight then used it when I landed and turned off Airplane mode.
As a solo traveler precaution, I had another phone with me that I subscribed to the Telus Roam plan, but I never ended up using the phone as it always stayed in my hotel room except for travel days..

Your iPhone 15 will support one as long as your service provider has
not locked the feature.

Since you have a Canadian phone and plan you won't have to worry about your phone being locked. Telecommunications companies aren't allowed to lock your phone.

We used Vodafone. Check though that your phone does have esim capabilities. If so, one you get to the UK, find a Vodafone site and they'll set you up.