Disposable income for working households in Britain has fallen by £1500 in the past two years. The "median equivalised disposable income" for non-retired households fell between 2009/10 and 2011/12 from £27,176 to £25,671, a reduction of £1505.
The latest data on family income and spending from the Office for National Statistics (ONS) shows that since the economic downturn in 2008, median household income for the overall population fell by 3.8%, after adjusting for inflation. The median income for non-retired households fell by 6.4% while that for retired households grew by 5.1%. This is probably due to pensioners receiving benefits such as the annual winter fuel allowance as well as the annual upgrading of state pensions.
If you want to know where your declining cash goes to, here is a grim info graphic from the ONS.