Europe battles worst arctic blast in 25 yrs.

So severe, and so soon. From the Muscovites in the east with the flaps of their shapki, or fur hats, unusually turned down, to the Britons in the west with their ``wellies'' (wellington boots) pulled on to negotiate deep snow drifts, Europe is gripped in the icy clutches of its worst winter weather in 25 years.

What has surprised Europeans has been the ferocity of the polar weather so early in the winter calendar. The bitter cold and heavy snows that have caused traffic chaos, closed down schools, and marooned villages in many European countries have been blamed for more than 100 fatalities.

The concern now is whether energy sources, on which unprecedented demands are being made, can hold up through a bitter and prolonged winter. Energy cutbacks

Romanians in minus 22 degrees C. weather have already had to cut back on their central heating. In the Soviet Union, fuel demands have doubled and some apartment blocks in Moscow where temperatures are even colder - around minus 30 to 40 degrees C. - have gone without heat. The Soviet Communist paper, Pravda, reports that more than 25,000 freight cars are stalled on the tracks and coal deliveries stalled.

Both Soviet and Hungarian troops have been called out to assist in the relief operation. In Hungary, helicopters rescued stranded motorists and bus passengers. In Sweden, which has been every bit as cold as Siberia - and in some instances, such as minus 52 degrees C. in Nattavaara, even colder than that - there has been speculation that there will have to be energy cutbacks.

Britain - which is not as cold as the Continent, but whose homes are said to be colder - is experiencing unprecedented heating demands, and warnings that there may be cutbacks in heating supplies if the high demand persists. At least 20 people have already died in Britain from the excessive cold, accompanied by vast snow drifts that build up faster than snow plows can remove them.

Throughout Europe, temperatures have dropped to levels never previously recorded.

Scandinavia, for instance, is expected to be experiencing its coldest winter on record; the Soviet Union its coldest January. Meanwhile, capitals such as Copenhagen, Helsinki, and London have all experienced their coldest nights in 25 years or more.

The arctic weather has had several important consequences.

European fuel demands, which are a key factor in determining the price of oil, have been heavy enough to send the price of oil above $19 a barrel - the highest it has been in over a year. While this raises fuel costs for Europeans, it will benefit Britain and Norway, which are North Sea oil producers. Politics in the deep freeze

The icy weather has also served as a political deterrent, prompting the cancellation of a proposed one-day underground transport strike in London, and facilitating the collapse of public-sector strikes in France. Paris has already opened up two Metro stations to take in the homeless, while London is considering a similar move to protect its homeless, some of whom can be seen on the Victoria Embankment forlornly trying to stave off the cold weather with cardboard screens.

One British couple, meanwhile, found a way around the insulation problem.

They built - and then moved into - an igloo.