Hundreds of motorists spent several hours stuck on roads in Devon
Severe weather warnings are in place again for most of the UK as plunging temperatures lead to icy roads following more heavy snowfall.
The Met Office warned of "widespread" ice on untreated pavements and roads and urged people to take extra care.
Fresh snow covered many parts of the country on Wednesday, causing more travel delays and cancellations.
Hundreds of schools did not open, while pupils taking exams endured difficult journeys on treacherous roads.
A woman died after falling into a freezing lake near Nazeing, Essex, while trying to rescue her dog.
Further freezing conditions are expected for Thursday night, followed by milder conditions and rain for the weekend.
Snow cut off the Dartmoor town of Princetown in Devon
A flight taking more than 60 rescue experts, equipment and search to earthquake-hit Haiti was first to take off when Gatwick airport's runway reopened at 1515 GMT, having been closed all day.
Some rural communities remain cut off, while others are coping with power cuts, water leaks, increasing numbers of potholes and cancelled rubbish collections.
Prime Minister Gordon Brown has pledged a full review of the arrangements for keeping Britain moving during severe weather.
At Commons question time, he paid tribute to workers and volunteers for maintaining the transport network during "the worst weather for 30 years".
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"It does prove that Britain works best when Britain works together," he said.
Tory leader David Cameron said the pressure on road salt supplies showed lessons had to be learned from the severe weather.
The Highways Agency and councils are cutting salt use by half - up from the 25% agreed last week - to protect supplies.
Mr Brown said one UK salt producer had announced it was stepping up production, while imports were expected in the coming days.
He said the government was confident it would be able to "maintain the road network".
The Local Government Association said no councils in England and Wales had run out of salt, despite facing freezing conditions for a third week.
It said this showed they had been well prepared because recommendations suggested storing only six full days' gritting capacity.
Meanwhile, Communities Secretary John Denham has said people should not let "myths about litigation" prevent them helping out with acts such as doing elderly neighbours' shopping or clearing paths.
Snow did not deter joggers in Green Park, central London
The M48 old Severn Bridge has reopened after being shut overnight but the A66 in Cumbria and A628 in Derbyshire remain closed.
Runways at London City, Birmingham International, Southampton and Cardiff airports have reopened after a morning of delays and cancellations. Heathrow Airport reported 84 flight cancellations.
Most schools were open for students sitting A-level, AS-level and GCSE exams but many were closed to other pupils.
Geraint Edwards, who runs a climate station in Wales for the Met Office, said the snow was the worst he had seen in more than 30 years.
Speaking from the Berwyn Mountains, he said nearby roads were buried beneath 6ft (1.8m) snow drifts.
The mountain, it's like cream isn't it, there's hardly any black to be seen on it
Geraint Edwards
"I'm at the front door now, and I'm looking on the mountain and there's hardly a blade of grass to be seen," he said.
"The mountain, it's like cream isn't it, there's hardly any black to be seen on it."
England's south-western counties were also badly affected. In Gloucestershire, where snow ploughs were clearing two feet of snow on some routes, 215 schools were shut.
Black ice
A further 300 schools closed in Herefordshire and Worcestershire, with several roads impassable. Ambulance crews reported difficulties and
one team had to be rescued
from snow by a 4x4 vehicle.
Similarly, in West Yorkshire,
two vehicles hit buildings
and a taxi slid down an embankment onto a factory roof. Some 187 West Yorkshire schools are shut.
Yorkshire Ambulance Service said there had been a four-fold increase in calls during Wednesday morning.
Many bin lorries have been unable to carry out collections
Recent school closures prompted university admissions service
Ucas to extend its application deadline
for pupils at weather-hit schools by a week to 22 January.
BBC weather forecaster Tomasz Schafernaker said affected areas had seen 5cm (2in) of snow on Wednesday.
"It will be moving away northwards and as it does it will get lighter. With temperatures dropping, it's all going to refreeze so ice will be a major hazard."
Northern Ireland and Scotland - with the exception of the far north - had been milder, he said.
Temperatures across the UK are forecast to rise from Thursday, although snow could return next week.
Police have admitted they were caught out by a blizzard which left
hundreds of people stuck for hours
on Haldon Hill and Telegraph Hill, near Exeter, on Tuesday evening.
Many forces were advising drivers to stay off the roads for all but essential journeys on Wednesday:
Sussex officers were called to about 70 incidents, such as minor crashes and stranded cars blocking roads, while there were 70 crashes on Wednesday morning in Derbyshire
Bus services in many snow-affected areas have been suspended
Twelve train operators - including Eurostar - report disruption. Buses continue to replace East Coast trains between Edinburgh and Motherwell, and Inverness and Perth
Virgin Trains services between London Euston and stations on the West Coast Mainline were delayed by up to 100 minutes after power lines were brought down
People in Cockermouth, which was devastated by the floods that hit Cumbria in November, have said leaks are causing fresh misery.
Icy conditions have also prevented bin lorries making collections on some roads, with Kent, Merseyside, Cheshire and North Wales among the areas affected. Households in some areas have had rubbish mounting for three weeks.
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