There are around 24 million dwellings in England and Wales and of these over 750,000 are empty.
Many of these are in private ownership and many of these properties will be unsuitable for short term use for a variety of reasons (for instance, they may be in the wrong place, require too much money to make them habitable or simply not be available for long enough), but nevertheless there will be many that are suitable. .
Private owners, housing associations, local authorities and other public bodies all own property that could be used. It may be housing that is awaiting improvement or redevelopment or housing that has been designated for other uses such as roads, schools of other public buildings. Either way, if there’s a delay then there’s often an opportunity to bring it back into use. .
If you’re interested to see what the national picture looks like, broken down by local authority in terms of housing stock and the number empties, then follow this link to get the latest government statistics as at 1/4/08.
You will also find a lot of useful information on The Empty Homes Agency website – www.emptyhomes.com 
If you want to understand better the situation in your own area then you may find that your local authority has an Empty Property Strategy which sets out the extent of the problem and how they envisage tackling it. Don’t be dismayed if there’s no reference to self help housing – it may not have occurred to them as an option!
A good example can be found in this strategy document from the London Borough of Islington , which sets out their approach.