Few countries so consistently turn out handsome stamps as Great Britain, and fewer still can get so much meaning into such little space.

Britain has been doing this year after year, but it has been particularly noticeable on most of this year's issues, in which complex subjects have been given clarity and vividness through the use of innovative designs, lavish use of color and high quality engraving.

In one recent issue, the problem was marking time -- Greenwich mean time, universally used in navigation at sea, in the air and in the exploration of the solar system.

The commemorative occasion was the 100th anniversary of an international conference in Washington that adopted the Greenwich meridian as the zero of longitude. The conference was swayed by Britain's long history of exploration and navigation, by the presence of the Royal Observatory at Greenwich, which was the source of a nautical almanac universally used at sea, and by the United States and Canada having already adopted the Greenwich meridian.

The set of four stamps goes from the present and the future to the past of a century ago. One pans in on the meridian from space, showing a picture of Earth taken from their spacecraft by the Apollo XI astronauts on their pioneering flight to the moon. Houston mission control used Greenwich mean time to direct their observation.

The oceans are represented by a stamp showing a navigational chart of the English Channel. This is followed by an encompassing aerial view of the facilities of the Greenwich Observatory. Finally, there is a representation of the transit telescope designed by the Astronomer Royal, Sir George Airy, that has been used for more than 100 years to make accurate observations of the solar system and stars.

The unifying and identifying element on the stamps, which differ widely in style and scope, is a red line focusing on Greenwich that represents the meridian. There is a real brass line in the courtyard of the observatory that separates east from west, sets up time zones and distinguishes lines of longitude; it is the embodiment of the Greenwich meridian.

From outer space to inner city and urban redevelopment is a quantum leap. But Britain handled a subject usually associated with prolix statistics and charts equally, if not more, imaginatively. This was achieved on another eye-catching block of four that used novel design elements to add interest and a good dash of philatelic flair.

Each stamp of the block uses a partially rolled-up architectural drawing as a curtain that reveals a partial setting of restored and beautified areas in four of the nation's big blighted cities -- Liverpool, Durham, Perth and Bristol. The squares and circles of the architectural renderings are distinct, and the angle of the rolled architect's plans focuses the eye on what the squares and circles really are.

This quartet, and also the Greenwich mean time quartet, has been produced by gravure in six and seven colors that make them stand out visually in the realm of stamps.

A se tenant strip of five for the 200th anniversary of the first mail coach run from Bath and Bristol to London attests once again how well British stamps recapture the past, especially a past so rich as Britain's. The mail coach, at a 12 miles-an-hour clip, was the epitome of swift communication and a turning point in British postal history. It reigned for little more than a half century.

The stamps, produced by gravure, reflect in their illustrations and design the work of 18th-century artist James Pollard. The historical impact is also carried out by the use of black, slate black and light stone tint that makes the stamps look like etchings. In addition, the sketches were engraved by Czeslaw Slania of Sweden, the world's foremost engraver.

The strip of five depicted in sequence the original Bath mail coach of 1784, an attack on the Exeter Mail in 1816, the Norwich Mail in a thunderstorm in 1827, two coaches of the Liverpool Mail in 1828 and the Edinburgh Mail snowbound in 1831.

In its concluding issues for 1984, Canada has put out a set of four commemoratives for the oldest lighthouses on its two oceans and its waterways, another set of four continuing its series on vintage locomotives, a tribute to the longtime editor and publisher of the French-language newspaper of Montreal, La Presse, and a tribute to the Royal Canadian Air Force.

The stamp honoring Treffle Berthiaume, the moving force of La Presse, has a photograph of him with his familiar bowler hat created out of different shadings of the name La Presse set in five columns of black type against a newsprint background.

Another single stamp pays tribute to the Royal Canadian Air Force and features pilots in flying garb of three different periods: World War I, World War II and the present.

For information about new issues or for placing orders, there is a new address. Collectors should write to Philatelic Service, Canada Post Corporation, National Philatelic Center, Antigonish, Nova Scotia, B2G 2R8, Canada.

There are no first days of issue scheduled for December by the United States, the United Nations or Canada.