This refers to my personal circumstances and as you well know it all depends on your provider and what phone you have.
Being with O2 I get free EU roaming but when going outside that area I'm slapped with over £7/mb.
Because my phone have e-sim capability (I believe most newer phones do) I can take advantage of the innumerous e-sim data only providers.
My personal choice goes to www.Bytesim.com which offers great value for money.
For my next trip during the Xmas break I've bought 20 days @ 1gb daily allowance for under £18
Still getting to grips how the thing actually works and how the e-sim is installed.
For the look of it, it needs to be in the destination country (or countries if you go for that option) and once you have installed the sim it will automatically turns off your UK card and operated on the e-sim.
Yes, there is no phone connection on that sim. however, you can use chat apps like WhatsApp or any other data based app and still be in touch with whoever you want.
I find this quote handy to be able to use. Hence sharing the information