Travel to the UK sim card provider?

[T56impala]

I have an Iphone7, unlocked, specifically for travel. I will be visiting the UK in a few weeks. I'm from the US, would love to text and send photos back to the US for the 23 days I'm there. Which providers card should I pick up? Who has the best data deal? I'd prefer to pick up the card at the airport before i start my travels. (I also need to be able to be contacted by phone but that's not my priority.)

Any suggestions?