I’ve been with ID mobile for a few years now. What I like is they include 30GB per month data when in the EU. We pay £10 per month each for unlimited calls and texts, and 100Gb UK data. They also roll over unused data for one month in the UK.
if you look on Martin Lewis’ SIM Finder on his website, you will find even better deals. I’m looking at one for my daughter that gives unlimited calls and texts, 120Gb data and 30Gb roaming data for £10 per month but with a £65 Amazon or Currys gift card for signing up. Not a bad deal at £55 over 12 months after taking off the gift card.
My phone supports dual Sims, so the other thing I’ve done is change over to an eSIM with ID mobile (free of charge) and that will allow me to buy local SIM cards if I need extra data while away in Europe. Last year I used up my 30Gb roaming allowance but then I bought an Orange SIM card while in Spain that gave me an extra 100Gb of data per month throughout the EU for 20 euros per month. There was no contract; I just bought a month at a time.