London — Across these British islands, the holiday period has brought surprisingly warm weather, and the customary British mix of holly, turkey, dark fruit cake, long family walks, slapstick pantomimes, television films, and a cinema dominated by Stephen Spielberg's lovable ''E.T.''
It has also brought its annual fair share of paradox.
Despite stubborn economic recession and massive unemployment, retail shops have done a roaring pre- and post-Christmas trade, much of it in imported goods. People have had more money in their pockets because of falling inflation, lower interest rates, and two reductions in mortgage rates (which are variable here) toward the end of the year.
Even record unemployment helped cash registers clang more loudly. ''Redundancy'' pay (severance payments) has totaled several thousand pounds for laid-off workers with long service records. Companies contribute to a government scheme which sets severance pay levels at which the government reimburses company pay-outs.
Friends report large sales of luxury BMWs and other sedans in high unemployment areas in Wales and elsewhere after coal mines and steel factories closed. Some blame the British system of unemployment relief: If a man has $:2, 000 ($3,250) in the bank, his regular dole payments are much less than if he has a smaller savings balance.
This encourages many to spend their severance money on paying off mortgages and on Greek cruises, then to collect higher twice-weekly dole checks. Some see nothing wrong in this; one Leicestershire businessman deplores it: ''The system should encourage people to save, not spend,'' was his view.
More paradox: Prime Minister Margaret Thatcher continually exhorts Britain to work harder and produce more. Yet, as usual, large segments of the economy practically closed down for two weeks.
This year, with a Christmas and New Year's Day both falling on Saturday, Dec. 27 and 28 were declared bank (official) holidays, as were Jan. 3 and 4. Since Britain has some of the highest domestic energy costs in Europe, many factories find oil, gas, and electricity much too expensive to open up for two short working weeks in a row. The result: Many a worker who began drifting home around lunchtime Dec. 24 will not return until Jan. 5 - 13 days later.
Pundits, the press, radio, and television proclaim bad economic news on all sides in Western Europe. Yet a year-end Gallup poll conducted in 31 countries for the national Daily Telegraph newspaper actually finds British people more optimistic than in recent years.
Three years ago a similar poll found Britain the most pessimistic of all about prospects for the next year. This time, Britain is eighth most optimistic in reply to the question: ''Will 1983 be better for you than 1982?''
Optimists outweighed pessimists by 41 percent in Greece, 37 percent in South Korea, 30 percent in Colombia, and 18 percent in the US.
Next came Brazil, India, and Britain, where the optimists were 13 percent ahead of the pessimists. Then followed Canada, Chile, Norway, Japan, and the Philippines.
This made Britain the second most optimistic nation in Western Europe (behind Greece) and markedly more optimistic than West Germany (where optimists lagged 9 percent behind the pessimists) Finland (10 percent behind), Sweden (13 percent), Portugal (15 percent), France (an interesting 24 percent), Italy (29), and Ireland, Holland, Denmark, Austria, and Luxembourg (all above 30 percent). Belgium was remarkably pessimistic, with optimists a full 53 percent behind.
The figures should not be taken with the utmost gravity. For what they are worth, however, they do appear to indicate that Western Europe's prolonged economic recession (current predictions are for 20 million out of work by mid- 1984) is sapping public confidence in the immediate future.
They also suggest that British unemployment payments, which are close to and in some cases higher than basic wage rates, are cushioning the impact of unemployment here, while for those with jobs, prospects have looked up as inflation has gone down.
Meanwhile, nonseasonal issues creep into the news.
The Archbishop of Canterbury, Dr. Robert Runcie, preached a Christmas sermon in which he said that full-scale nuclear war was unwinnable. All talk which made nuclear war seem anything else but ''madness'' should cease, he said.
But he is disturbed at constant, almost casual talk of war. So is the Archbishop of York, Dr. Stuart Blanch, who warned of nuclear devastation in a recent diocesan leaflet.
Some right-wing Conservative members of Parliament criticized Dr. Runcie for what they thought was support for women camping outside a US base at Greenham Common near London. The women have gained wide publicity protesting against 96 NATO cruise missiles to be installed there. They are a symbol of the growing Europe-wide peace movement which NATO governments see as a serious political threat to cruise and Pershing II missile deployment against the Soviet SS-20 missiles aimed at Europe.
In fact, Dr. Runcie did not criticize government policy, and the Bishop of Durham, John Habgood, said Dec. 28 that some Tory members of Parliament had overreacted.
The synod of the Church of England is to consider in February a controversial study report called ''The Church and the Bomb,'' which calls for Britain to give up its nuclear weapons because they are ''immoral.''
Sources including Dr. Habgood say the synod will certainly not adopt the report as church policy. Other milder resolutions will be offered against it.
Also causing headlines over the holiday period was the leader of the opposition Labour Party, Michael Foot. He has long called for an end to British nuclear weapons, and his party is pledged to unilateral disarmament if returned to power at the next election.
Mr. Foot visited the Greenham Common protestors the evening after Christmas Day with his wife and dog. He gave them cheese as well as his own personal support.
Mrs. Thatcher recognizes the genuine motives of the protestors, but considers their actions to play into the hands of the Soviet Union.