They have the UK at $1 billion ( External Link/Members Only ), whereas that £5.3 billion, at 2009 prices, is getting on for an order of magnitude larger. So maybe their figures aren't particularly reliable.
I reckon I spend 3x what the Spanish average is and I am a cheapskate
How on earth would anyone calculate the undeclared cash expenditure to prossies or their undeclared income
Indeed - all their figures may be unreliable!