Used Virgin Media WIFI?

Mike, what kind of phone service do you have at home? If it is unlocked (Verizon phones should be unlocked), you can just buy a SIM when you get to the UK.

A "media WiFi" or "hotspot" device uses the same technology as a cell phone - it just has a SIM card inside like a phone does. If it works in the tube, so will a phone.

I've used Google Maps constantly when roaming around European cities, and I still use only about 120mb/day or so, sometimes less. But I don't stream videos or do video chats unless on WiFi - video eats a lot of data.

Are you referring to station WiFi?

https://tfl.gov.uk/campaign/station-wifi

If so, it appears you’re not limited to Virgin Media.

"I am concerned about running out of cellular data or overage charge."

How are you obtaining this cellular coverage, how much is it costing for the regular charge, and how much do you get before you incur overage charges?

I have Verizon, and on my last two trips to London, i have used the $40/100min, 100messages, 100mb plan. I found that I was able to simply turn off data and rely on the readily available wifi all over the place. I never turned on data.

I have Verizon, and on my last two trips to London, i have used the $40/100min, 100messages, 100mb plan. I found that I was able to simply turn off data and rely on the readily available wifi all over the place. I never turned on data.

If you never turned on data, then you probably wasted $40; you probably could have used WiFi calling on your phone to get texts and make phone calls for free. You could have spent the $40 (or less) to buy a local SIM card and get the full use of your phone for walk-around navigation, something that has saved me a lot of time and frustration over the last few years.

Well... for your interests it might have been a waste for you. For myself, I am quite capable of assessing my own needs, the services I know I want and spending my own money as I see fit. That $40 was spent just fine.