Ice alert following days of snow
More snow is predicted as ice is expected to cause chaos on the roads
People are battling with treacherous conditions after sub-zero temperatures followed days of heavy snow to leave icy roads and pavements across the UK.
Thousands of schools remain shut and transport disruption continues.
UK-wide severe weather warnings of ice are in place, with temperatures staying near freezing. Conditions on side roads are a "nightmare", forecasters say.
Temperatures fell to -18C overnight in places and the Arctic conditions are expected to continue for up to a week.
About 7,000 homes across southern England are without electricity because of trees falling on power lines and safety mechanisms being triggered by ice weighing down cables.
Up to 25,000 homes have been similarly affected since Wednesday.
A Eurostar train from Brussels to the UK broke down in the tunnel at 0830 GMT, a company spokesman confirmed.
WEATHER AND TRAVEL INFO
Get the latest on school closures and travel problems via your BBC Local website
Check if snow is forecast in your area at BBC Weather
Details of motorway and local road closures and public transport disruption are available at BBC Travel News
For advice on handling difficult driving conditions, see the Highways Agency website
For information about severe weather warnings, see the Met Office website
For information about staying healthy in the current cold snap, see the NHS Winter Health website
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A Eurotunnel rescue train had towed it to Ashford in Kent by midday. Eurostar was already running a restricted service, with four trains cancelled, and further delays are expected.
All major airports, including those previously affected by snow such as Glasgow, Luton, Birmingham and Cardiff, are operating but passengers have been warned to expect delays.
Budget airline Easyjet has cancelled nearly 70 flights on Thursday, mostly at Gatwick where 136 inbound and outbound flights were cancelled. Forty people worked overnight to de-ice the runway.
British Airways has also cancelled some flights.
On the railways, 20 operators' services are disrupted. East Coast has advised passengers not to travel between Perth and Inverness.
Virgin Trains has cancelled several services between London and both Manchester and Birmingham.
Southern Trains warned of "severe disruption", while First Great Western has cancelled several high-speed services between London and Cheltenham, Bristol and Cardiff, along with many local routes.
First TransPennine Express was reporting delays and suspensions on many routes, while signalling problems at Northallerton were snarling up the network in North Yorkshire.
Several councils around the UK are limiting gritting to major roads, as salt supplies are stretched.
Salt shortage
Transport Minister Sadiq Khan said the government was working with local authorities, devolved administrations and the highways agency to help salt suppliers prioritise deliveries.
He said the equivalent of 600,000 miles of road had been gritted in the last two weeks and that the Highways Agency went into the winter with 13 full days of gritting capacity.
BBC Radio 5 live's travel reporter Nick Duncalf said conditions were so cold that grit may have no effect, although most major routes were "fairly under control" on Thursday morning.
HAVE YOUR SAY What happens if this weather stays with us for 3 to 4 weeks?
Snowman, Essex
Send us your comments "Everybody knew it was going to be cold and icy and, on motorways in particular, traffic levels are fairly light," he said.
There were delays on the M20 in Kent, caused by a jackknifed lorry and fuel spillage, and on the M5 in Worcestershire after an accident. The A66 in Cumbria and A628 in Derbyshire remain closed.
The north-south A470 in Wales is closed between Rhayader and Doldowlod, Powys, after a crash.
Poor driving conditions also closed routes including the A542 Horseshoe Pass near Llangollen, Clwyd, and the A4233 and A4061 around Merthyr Tydfil, mid-Glamorgan.
A teenage boy died and his mother was seriously injured when they were hit by a lorry after leaving a car that had crashed on the A1 in North Yorkshire near Scotch Corner on Wednesday night.
A 42-year-old man died further along the road when his car crashed with a lorry south of Cockburnspath in Scotland.
The widespread school closures which saw some 10,000 shut across the UK on Wednesday have continued, including:
about 950 in Wales
at least 250 in Scotland
more than 900 in Bedfordshire, Hertfordshire and Buckinghamshire, 250 in Oxfordshire, 380 in Surrey and 600 in the Solent
at least 500 in Kent and 200 in Essex, along with 560 in East Anglia and 160 in Sussex
more than 1,300 across north-western England
about 390 in north-east England, as well as at least 250 across Yorkshire
more than 1,000 across the South West, along with the University of Bath
The Federation of Small Businesses has criticised head teachers for closing schools too readily, saying lost working days affect many companies.
Overnight temperatures plunged to a low of -18C (0F) in Woodford in Greater Manchester and Benson in Oxfordshire. Monitors recorded -13C (9F) in Manchester, -6C (21F) in Glasgow and - 3C (27F) in central London.
Up to 5cm (2ins) of snow is forecast for eastern England through Thursday, and snow showers are also possible in Aberdeenshire, the Midlands, the South East, Pembrokeshire and Cornwall. Stronger winds could lead to some drifting.
Maximum temperatures include 0C in Glasgow, -1C in Leeds and Birmingham, and 1C in Cardiff, central London and Belfast, while overnight it could drop to -20C.
BBC weather forecaster Liam Dutton said: "Ice will be the main hazard for most people today. Side roads will be a nightmare."
Sporting fixtures continue to fall foul of the weather, with race meetings at Kempton and Lingfield called off and the weekend's racing, rugby and football fixtures under threat.
