Airalo etc.

Calls will be fine. Data with T-mobile is slow but works.

I tried Airalo and couldnt' get it to work at all in Scotland. I called their tech department via wifi calling in my hotel and they couldn't figure out why it wasn't working. I got a refund.

I also have an esim from Roamless and it's no better.

If you want to use an esim in the UK, it may be best to get one from a UK company.

We used Airalo November 2024 in Egypt, Jordan, and Qatar (regional plan) with no problems. Worked like a charm.

March 2025 in New Zealand, Airalo worked fine for about two days then stopped working on both our phones, had to switch to a New Zealand-branded phone company (Spark).

Here is a thread I posted about cell service on a recent trip to London. If you run into that same problem, there are some potential solutions you could try and a few other ideas that might be helpful. https://community.ricksteves.com/travel-forum/england/mini-trip-report-about-terrible-cell-service-in-london

You can buy additional service from T-Mobile. I will definitely do this next time, as I often relied on my AT&T friend's data on our recent trip. Here is the info:
https://www.t-mobile.com/cell-phone-plans/international-roaming-plans/unlimited-calling-data-pass?icid=MGPO_TMO_U_TMOTRVLBNF_5ZF01OH0YUMZY4LHD29981

I’ve got an older T-Mobile plan that only includes slow data. The last 3 years I have bought the add-on international pass to get high speed data (mentioned above). In general, T-Mobile has worked fine, although on one occasion I had some issues in London with data dropping out.

When you arrive and turn on your phone, you will get a welcome message. The welcome message will include a link to upgrade if you decide you need to do that.

Good Day Ken,

I don't have T-Mobile, so I cannot vouch for quality of the service. However, on Airalo, I have some feedback.

I purchased the Airalo Data/Text/Calls eSim for my unlocked iPhone for my 10 day trip to London/Bath in December 2024. I mainly used it for data, but occasionally needed to make some calls and it came in handy. Data and call quality was good. It cost me $8.50 for the 15 day plan which provides 2 GB data, 20 minutes of calls and 20SMS texts. There is a less expensive option for 7 days for 1GB, but my husband is addicted to his streaming and I always need more data.

If you only use data (which I normally do and use What'sApp for connecting), then you can get a data only package starting at $5.00 for 1GB.

Note, you install Airalo before you arrive in the UK and select it as your primary and when you land and switch off airplane mode, it will automatically connect to the local carrier.

I’ve had no problem with T-mobile overseas. I mostly use data when driving from place to place using Google maps. Websites will load slowly, so I usually visit them when connected to WiFi. I seldom need to make a call overseas (haven’t made one in about 7 years). If I need to make a quick call, the .25 a minute wouldn’t be a budget buster. Again, if the call can wait, I’ll make it when connected to WiFi. I use texts when communicating with those back in the states.

a few words of caution:

we used Airalo ~ 6 months ago in France for about 2 weeks.
installation on one phone was easy, on another had a small hiccup but both phones worked when we arrived in France.
outside Paris, we found the service spotty, especially outside medium size cities. Cell service was so spotty that we couldn't reliably use google maps or google translate.

we also found that adding additional GB data was not easy; after contacting AirAlo with multiple failed attempts their solution was to sign up for a new plan. Since AirAlo re-markets data plans from different cell providers, it turns out that the airalo had changed cell providers from the time we originally signed up and the time we needed to add more data. contacting AirAlo through their app was not easy; eventually they replied to an e-mail.
(even though we didn't use a lot of data (because of the aforementioned weak service, when we were in Paris for the final days of the trip we ran out of data; it turns out that geotagging phone photos automatically saves/syncs them to the cloud, which uses up a lot of data.)

so sign up for a larger plan than you might think you need.

I've used Airalo frequently over the last 3 summers in a bunch of countries. This year I had trouble in the UK initially; I downloaded and activated an eSIM, but it wouldn't ever connect. After cursing Airalo for multiple days--during which I used the higher-cost data provided by my regular Google Fi plan--I decided to read through the installation instructions. I'm embarrassed to admit I apparently didn't do that after purchasing the eSIM.

It turned out that my current Airalo UK eSIM set-up process requires an extra step, different from most of the other Airalo eSIMs I've used. Once I followed that simple step, everything was fine.

User error strikes again.

it turns out that geotagging phone photos automatically saves/syncs them to the cloud, which uses up a lot of data

Backing up photos and videos to a cloud account can use up significant data. On iPhones you can control most of the apps that use cellular data. Go to settings>>>cellular you should see a list of apps that you have cellular data usage enabled. Toggle on off as needed. For iPhones having location services turned on to geotag photos does not automatically enable using cellular data for backups.

My wife and I are Tmobile customers. On a recent Ireland tour, she bought the $50 add-on for high speed data. I did not. I actually had no problem with the 256 kbps slow data. I use a simple map program, "Organic Maps". I download the maps when on wifi, and need no cell data. However, it doesn't give directions (I just read the map). I mostly communicated with texting, had no problem. I did notice that when texting a photo, it took a bit longer to send it, but no big deal to me. Coverage was good.

Incidently, it was the same for us in Switzerland, the slow data worked fine for me.