• If you decide to buy a new TV or recording equipment, look for the
  digital tick logo. It means the product is designed to work
  during and after switchover.
• Some high definition (HD) TVs may not be digital-ready – look for
  the digital tick logo (as here on the right).
• If you are not sure if your HD TV is digital-ready, contact
  a trusted retailer or the manufacturer of the TV.
• You do not have to buy a new television set unless you want to - nearly all current TV sets can
  be converted by connecting to a digi-box.
• You can test your current aerial to see if it should work with digital Freeview, or needs replacing.
  The test pattern is broadcast on Teletext page 284 on BBC1, BBC2, ITV1 and Channel 4 and
  page 484 on S4C. You should carry out the test on all channels and under different weather conditions.
  Ideally, the screen should display a full grid of vertical/horizontal white boxes. If there are more than
  4 squares missing (randomly spaced – complete lines missing are fine) then your aerial needs to
  be checked and maybe replaced.

The map (courtesy of UK Free.TV) shows the planned shutdown for analogue TV transmissions across the UK. The red areas show the analogue signal coverage; the yellow shows each ITV region and when transmissions will switch to digital in that region. The map turns from red to green to show the spread of digital coverage across the country, through to 2012.

If you are receiving Freeview currently, you will continue to receive the full package of channels after switchover. This is estimated to cover 73% of the UK's population. If you cannot receive Freeview currently, but you watch analogue TV from one of the 80 main transmitters, you will be able to view the whole Freeview package. However, you may need to upgrade your aerial to a wideband type, or relocate a loft-mounted aerial to the roof.
If you are not receiving transmissions from one of the main 80 TV transmitters, you will be able to view the three public service multiplexes after switchover, but you may need a new aerial. This applies to 8.5% of the UK's population, about 5 million people.
The 1.5% of the population (a little under a million people) who do not currently receive terrestrial analogue TV will not be able to receive digital terrestrial TV after switchover [source: UK Free.TV]