Council Tax Freeze

So George Osborne has managed to find an underspend in Whitehall of £800million has he?  Is that on top of the cuts which he expects all public services to find?  If so, has he really thought about what £800m could do for the country?  An average saving per household of £72 in a year, or a little over £1 a week will hardly be noticed in most of those homes.  Being able to afford an extra loaf of bread in the supermarket won't exactly be a huge boost to the economy or save many jobs.  But imagine investing that money in a handful of UK companies in an area like the North East - maybe companies producing solar panels so that we don't import so many from China and Korea?  Maybe companies producing insulation for solid walled houses, bringing the price of the goods down to affordable levels for more people?  Maybe even invest some of it in social housing to make sure that solar panels and top quality insulation are available to those properties too?  Jobs are created here in the UK, fuel poverty is decreased because more people can benefit from better insulation and more affordable renewable energy and so those people can spend more of their money on other things and the whole economy benefits.
But I'm not an economist and I didn't go to the right sort of school or university so perhaps I'm just a naive dreamer who doesn't understand the way things work.  I do know that the ideas being floated at the Lib Dem conference on how to invest any extra funding didn't include freezing council tax, and I wonder how come £800m can be found in a fortnight!