The key adjective I placed before cartel re UK banks was "informal". Despite their crass stupidity when it comes to dealing with other people's money the CEOs etc. at UK banks won't want to spend any time in jail or cough up any of their own ill gotten gains so the way to ensure that they do this is by always matching each other, give or take a few days, when it comes to setting interest rates, offers etc. so that there is no real competition between banks but there is also no smoking gun in the form of phone calls, meetings or e-mails that would give away that they are running a cartel. The same applies to UK energy companies (the big 6) who amazingly all increase (but never decrease, no matter the wholesale price) their electricity or gas prices to consumers and petrol retailers. The cartels learnt their lesson long ago (e.g. when Virgin blew the whistle on British Airways, Virgin Atlantic)and others forming a UK airline cartel).
The banks also have the supposed regulators (previously FSA, now Bank of England) actually doing their work for them instead of protecting consumers which is doubly ironic. The regulators pretend to do something about the banks (levying pitifully small fines compared with turnover) whilst making absolutely sure that the bar is set so high that there can be no new entrants to the supposed "market" - witness the appalling obstacles placed in the way of "The Bank of Dave" aka Burnley Savings and Loans Ltd - see
http://www.youtube.com/watch?v=MjLEiR05o0I).
It's not just the banks to be fair, I used to work in the Energy Industry and having visited OFGEM's fabulously expensive HQ in London and witnessed how they fawned over the representatives of nPower etc. it's clear who's the puppet is and whose hand it is shoved up their backside.
I'd be happier if the banks, energy suppliers, petrol companies etc. were to just come clean and say "Look, you're all little people who we can't stand but we do want your money to fund our excessive pay packets so just hand over the dosh" - it would at least be honest.