But the purpose of an economic stimulus can't just be to move lumps of consumption around by a few months; I don't think that even in the current climate it's necessary to run a big sale in November purely so that you have the cash to pay the salaries for your shop workers in December.
So Alistair Darling's job is to make Britons more profligate than they are now for the next two years (despite the financial mess being, as far as I can see, a function of a decade of unbalanced profligacy) and more frugal than they are now for at least four years to follow. I don't see how subtle tweaks to the tax system can do this; indeed, I don't know if it can be done. Interest rates are the obvious instrument, but profligacy and frugality are functions of upbringing and circumstance in that order; after-tax interest rates on straight savings accounts are now below the rate of inflation, but this has meant that I grumble slightly, keep most of my money in just-as-insured short-term bonds, and devote slightly more to the stock market where there's a possibility of higher returns.
What government policy would make you go out and spend more in February?