Google Pay is out in the UK.

You'll also need a compatible bank and if you're with Barclays, Natwest or Santander you won't be in luck. Supported banks at launch include Bank of Scotland, First Direct, Halifax, HSBC, Lloyds Bank, M&S Bank, MBNA and Nationwide Building Society.
As i'm now stuck back on my old OnePlus One (Still a decent phone!) i'll be making use of this.

I've noticed Tesco Bank isn't on this list which is a shame. They have one of the best Mobile apps going in my experience!

Source:
http://www.techradar.com/news/phone-and-communications/mobile-phones/everything-you-need-to-know-about-android-pay-in-the-uk-1321615