Drivers are heading off on the big Christmas getaway as the freezing weather kept its grip on the country.

With many areas waking up to yet another icy morning, motorists heading home and out shopping faced one of the busiest driving days of the year.

The number of cars on the roads was expected to peak later on Thursday evening as people try and get home before Christmas Eve and out for some last-minute bargains, with the AA's Paul Watters warning: "We are building up for a problematic day on the roads."

Passenger backlogs at airports and on the trains have begun to ease, but critics are rounding on the UK's inability to cope with wintry weather. Much of the country saw temperatures fall below zero overnight, prompting widespread warnings for icy roads.

The majority of the UK should stay dry but cold, with slight snow showers in northern and eastern parts of the country. Weather-related troubles saw the motoring rescuers field an estimated 21,000 call-outs on Wednesday, and Mr Watters said: "We don't expect (Thursday) to be any easier."

Heathrow - which has made headlines for days as massive amounts of flights were cancelled due to snow and ice - said it was expecting to operate 1,206 flights on Thursday, almost a full schedule. After reopening its second runway on Tuesday, the gateway fulfilled two-thirds of its business the following day but stressed passengers should not expect an immediate return to normality.

BMI chief executive Wolfgang Prock-Schauer also claimed the airport "did not have enough de-icing fluid" - something a Heathrow spokesman strenuously denied, saying: "It is categorically untrue that we have either run out of de-icer, failed to order enough de-icer or accepted de-icer supplies from the Government."

Meanwhile under-fire BAA chief executive Colin Matthews announced he would forgo his annual bonus. Mr Matthews said: "I have decided to give up my bonus for the current year. My focus is on keeping people moving and rebuilding confidence in Heathrow."

After the Eurostar was crippled, a company spokesman said it was running 90% of its service. The travel improvement coincided with weather forecasters predicting relatively mild weather in the run up to Christmas Day.

Train travellers had to contend with delays and cancellations, with a number of London to Leeds East Coast main line services axed and some of the trains between the two cities also facing cancellation on Christmas Eve.

First Great Western cancelled some London to Cardiff services on Thursday, some ScotRail services were axed, First Capital Connect was running an amended timetable, while Northern Rail had to cancel more than 30 trains.