Before the most recent crash, the financial sector of the US economy represented 40% of GDP one year (and I doubt the UK was too far off from that). Clearly a ridiculous figure. While most of that was probably fees on stock trading and the like, some part of that was consumer financial services.
And besides, banks are a good place to start to modernize because they're already heavily regulated so consumers have more of a chance of pushing what's good for us. But once we prove the possibility and utility of digital fiances, imagine that instead of a piece of paper, you get a digital receipt for everything you buy. Imagine XML or JSON that specifies not just a total, but each line item, the quantity, the discount, the amount, and each tax it;s subject to. And imagine all that data being automatically and instantly received integrated into your personal financial app. You could know exactly how much ($ and %) you spend on gas, kids clothes, cheese, state taxes, local taxes, etc. You could get a history of your spending and see trends. All without any data entry.
Now imagine you and millions of others choose to share that data anonymously with some server somewhere. And imagine an app that, by knowing exactly how much and where other people have paid for things in the last few minutes, could tell you the cheapest way to buy everything on your grocery list. Willing to drive up to 10 miles? It has an even better deal. Willing to go to up to 3 stores? You can get it cheaper still! Want it delivered? Companies have already bid on it and there's a price for that too.
I don't object to either private companies or the government collecting data on everything we buy, everywhere we go and everyone we associate with. I object to them not sharing that data with me in a useful format. I can make way better use of it than big business or big government ever could. But if consumers and citizens actually had such data, real competition would mean both big business and government would be in a heap of trouble.