Snow and ice causes disruption as cold spell continues
Further snow and freezing temperatures are causing major problems for road, rail and air services in much of the UK, and thousands of schools are shut.
There are icy road warnings, and up to 15cm of snow could fall in some areas.
Many roads are gridlocked, some trains and buses have been cancelled, and Gatwick and Edinburgh airports will be closed until at least Thursday morning.
The Met Office has issued heavy snow warnings for much of the eastern side of Britain and some central areas.
In England, heavy snow warnings are in place for Yorkshire and Humber, the East Midlands and north-east England.
In Scotland the warnings apply to Grampian, Central, Tayside and Fife, Strathclyde, south-west Scotland, Lothian and Borders.
Thousands of Scottish children arae having a third consecutive day off as many councils keep schools closed.
Hundreds of skiers took to the slopes near Aviemore in the Cairngorms on Tuesday, and an avalanche warning has now been issued.
Supt Chris Moon of Surrey Police said the county's conditions were the worst he had ever seen and were likely to deteriorate further. He said people should not travel unless they had to, adding: "I have put out several severe weather warnings in my career, but this one I really must stress."
Police have issued the same advice in Kent and in South Yorkshire. In Kent some roads in the west and north of the county are impassable due to snow and ice.
Thousands of rail commuters face severe disruption to their journeys in Scotland and northern England - particularly in the Sheffield area. London and the south-east has also suffered, including delays and cancellations to Southeastern services operating out of London Victoria and Charing Cross.
There are delays on the East Coast Main Line, with an hourly service between London and Edinburgh, and reduced services between London and Leeds and London and Newcastle. Passengers face delays of up to an hour on Eurostar services.
National Rail Enquiries (NRE) has set up a phone hotline to information about snow-related disruption, on 08453 017 641, and also has updates at @nationalrailenq on Twitter.
One of the worst affected areas of England is South Yorkshire, where snowfall of up to 30cm (12 inches) has brought parts of the county to a standstill.
About 300 schools are shut, bus services have been suspended in Sheffield, Rotherham, and Doncaster, and there are delays and cancellations on train services between Sheffield and Leeds, as well as flights being halted at Robin Hood Airport in Doncaster.
Hospitals in South Yorkshire are asking patients not to attend unless it is urgent, and they have asked off-duty medical staff to make their way into work if possible. Meanwhile Sheffield City Council has cancelled its full council meeting for the first time.
All night train-trip
BBC weatherman Liam Dutton said up to 10cm of snow could fall in East Anglia and south-east England, with up to 15cm possible in north-east England and south-east Scotland.
"Temperatures will be barely above freezing across the UK and when you add in the effect of the wind chill, it will feel much, much, colder than that,