Monzo or Starling. Much are muchness between them. I have both, their features are very similar too. I prefer Starling for the fact that I can get a Business Account with it. In terms of rates they are the same for overseas purchases. Both have NPC wallet support, both have categories of spending and alerts etc.
I also have Revolut as well.
I've stopped using my Starling account. I just prefer the iOS Monzo app. Was in Thursday-Monday and Monzo is just great for travelling. Last few holidays I've been on it is nice not worrying about taking cash with me.
The only thing stopping me from going fully into Monzo now is that they don't have any benefits on their account like I do with my Natwest one. So at the start of the month I just transfer most of my income on to Monzo and just use that.