I use a local Sainsbury's....the small type. It's a weird L shape so there's a bank of tills in the short section and then a long bit where you queue....the "space" in the L is taken up with shelves.
MOST people begin queuing in the long section which is CLEAR....but there's always some numpty who stands in the wrong place when they're queuing....and if they're next, the whole queue has to go behind them down the narrow bit which is meant for those using the self service tills or browsing!
I am so British about it though that I'd never say "Excuse me...move to your left and queue there or we'll all be to cock in a minute when more people arrive."
So I meekly get behind them where I know I will be in the frigging way! Are you someone who queues WRONGLY?