I don't think that British shopper overspend by £30 at the till. I spend as little as possible on everything and I will leave items behind if the price is better one-where in another shop. I believe that most people don't over spend as money is so short they can't afford to over spend.
With the level of unemployment and people scared of loosing their job, along with the rising cost of electric, gas and Petrol. I rest me case.