More than 200 flood alerts are in place across the UK as heavy rain has mixed with melting snow.

There have been more reports of flooding in south Wales overnight as the downpours replace almost two weeks of snow. Norfolk police have reported flooding caused by melting snow and ice, which has closed a number of roads in the area.

Wales, central England, and the south-west will be the worst-hit areas, with at least 2.5cm (1in) of rain expected by mid-morning on Sunday, while the rest of the UK can expect around 1.3cm.

Rising temperatures of up to 12C have sparked a rapid thaw of the snow and ice which has built up in the recent cold snap, exacerbating potential flooding problems. The Environment Agency has issued 30 flood warnings urging people to take immediate action against predicted flooding, in the Midlands, the west of England, central England and Wales. A further 218 flood warnings are in place across England, Scotland and Wales affecting all but the east of England and north of Scotland.

Chris Burton, a forecaster for MeteoGroup, the weather division of the Press Association, said the heavy rain would return on Monday along with the risk of flooding, as the surface water and river levels build up before an unsettled week.

Around 18 buildings flooded in various locations across Wales on Friday night, including two houses in Solva, Pembrokeshire, and two in Dolgellau, north Wales.

The latest heavy snow storms on Friday night into Saturday left hundreds of people stranded for hours on motorways in the north of England. The M6 was blocked in both directions between junctions 25 and 27 in Lancashire when a sudden burst of more than a foot of snow brought drivers to a standstill from around 8.30pm, the Highways Agency said. Many became stuck along the stretch of motorway between Wigan and Standish after struggling to make it up inclines in the treacherous conditions, while a number of accidents including jack-knifed lorries also blocked lanes.

Mountain rescue workers were drafted in to help with rescue operations and check on the condition of drivers stranded by the snow. A diabetic man was taken to Royal Blackburn hospital after falling ill, while an ambulance taking a female patient to Royal Preston hospital had to be dug out of the snow by Bowland Pennine mountain rescue team.

Phil O'Brien, team leader of Bowland Pennine mountain rescue, said: "It was potentially a very serious situation. The Highways Agency managed to get people moving at about 4.30 to 5am [on Saturday]. There were hundreds of cars stuck but most people seemed in good spirits."

Some of the stranded drivers passed the time by having snowball fights and building snowmen, while others abandoned their cars completely.

David Cameron took to Twitter on Saturday to express his sympathy for those caught up in the snow.

He tweeted: "Huge sympathy for those affected by heavy #uksnow. Govt working closely with transport operators to minimise impact on everyone."

A family had to be evacuated when the gable end of their house collapsed, apparently under the weight of fresh snow in Barnsley, South Yorkshire.

The death toll during the recent cold snap, which is in double figures, is thought to have risen further as it was feared a man in his 30s or 40s might have frozen to death after going missing in woodland.

His body was found on Thursday night after four friends went to Newmarket police station in Suffolk reporting that he had not been seen for four days. The men had been searching for him and found him dead in a wooded area. The death is being treated as unexplained, but one theory is that he succumbed to the freezing temperatures.

A father died on Thursday when his car skidded into a river just before his wife's vehicle also plunged into the icy water. David Cox, 42, was taking his 11-year-old daughter Tess to school when their Toyota Aygo left the path and crashed into the river Wye in Derbyshire.

The children and their mother managed to get out of the cars and safely to shore but Cox was unable to escape.

Other casualties of the cold spell include the postman John Bircham, 57, who collapsed soon after he was towed out of a snowdrift in Dulverton, Somerset, last Saturday, and Bernadette Lee, 25, who was found collapsed in the snow in Deal, Kent, last Sunday following a night out.