Mobile data SIM for England in April

I bought a SIM card at “3”on Kensington’s High Street. Very nice store, helpful staff. I used it in London and Rome in December. Worked well. Our family used What’s App. Remember to change your phone number to SIM number in What’sApp settings.

I also had good success with a sim card from 3. 3 sim cards do not allow hotspots.
You can a 3 sim card via Amazon.
There are other outfits that will sell you data only sim cards that can be hotspots.
Make sure your old ATT iPhone six is unlocked. This no big deal unless you have to do it at the beginning of your trip.

You can go to a Carphone Warehouse, which is a store selling SIM cards from multiple providers. Just explain what you're looking for, and they can tell you the best deal.

As said above, if you want to use the phone as a hotspot, you need to make sure the plan allows it, and under what terms. For instance, my US T-Mobile plan allows unlimited hotspot data but only at 3G speeds, while my mother's T-Mobile plan allows her to use her 7 GB per month of hotspot usage at 4G LTE speeds.

Here's a link to the Carphone Warehouse page with their current pay as you go SIM-only deals: https://www.carphonewarehouse.com/sim-only/pay-as-you-go-sim.html

I wanted a SIM to set up in my "old phone" and keep active for return trips to Europe. I bought a Vodafone UK SIM while in the US and got it all set up, loaded with credit and a minutes/texts/data bundle. As it's from Vodafone UK, it would easily work in England. I used it in Germany, Poland and Czech Republic.

https://community.ricksteves.com/travel-forum/tech-tips/vodafone-uk-sim-card-for-use-in-europe

They also have pay as you go options, though I don't know if they allow using it as a hotspot.