Recently I switched to a new online-only bank called Monzo. It's fully licensed and all accounts are insured up to a certain amount by the UK government. It's great. They're in the top charts for apps in the UK now on the iOS App Store. There's a few other alternatives like Starling Bank and Revolut too.
They're very good. They're open about their tech stack with developer blogs and it's a modern stack which lets them iterate in a quick and agile manner unlike the legacy banks.
You get push notifications on every payment (usually you get the notification before the payment has even processed on the vendor's end!). Tells you exactly how much you've been spending every day.
They've got RESTful JSON APIs you can integrate with if you want to and they also have the option in the app to easily export your data into CSV or Quickbooks format. They even have IFTTT integration.
Really makes you manage your money better.