Another option is giffgaff, one of the UK's MVNOs operating off the O2 network. If you're in the UK, giffgaff is increasing the data limits for their £20 and £25 Goodybags (the term they use for their monthly plans) beginning February 26, 2020 from 40GB to 80GB. For the £25 Goodybag, you get unlimited but throttled data after 80GB. Both plans allow roaming data in the EU but limit that to a maximum of 20GB with a 0.36p per MB charge after that. When I'm getting ready to take a trip to the UK, Ireland, or the EU, I buy the £20 Goodybag (about $26 currently) just before I leave. When I get off the plane at my destination, my SIM is ready to go. I disabled automatic renewal in my account so by the time I return to the US, the plan expires shortly after, and I revert to a PAYG customer until my next trip.
They also allow topping up by a US credit card. If you're only planning to use the SIM for one trip, that's not a big deal, but I do yearly trips to the UK and Ireland with a trip to the continent thrown in every so often. Since you only need some minimal activity to keep the SIM alive--a text or a call every six months will do--it's easy to keep the number viable (friends, family, and work only need to program one number in, and it's good for any of my trips), and I don't need to buy additional monthly plans when I'm back here in the US. And Google Voice is always there as a backup.
ETA: Forgot to address one of your main concerns--giffgaff allows you to use your phone as a hotspot.
Last edited by lwildernorva; Feb 3, 2020 at 2:29 pm