WHAT IF THEY gave an anniversary celebration of the Battle of Yorktown (which the British lost, thereby ending the military phase of the American Revolution) and the British didn't come, figuring once at Yorktown was enough? That seems a possibility now as the 200th birthday of Yorktown looms. Understandably, the British prefer not to be reminded of the inglorious moment, when Lord Cornwallis -- with a French fleet off-shore and a combined force of over 17,000 French and American soldiers led by George Washington facing his lines -- surrendered his 7,500 troops.

Just as understandably, the French apparently could not be more delighted at a chance to participate in the Yorktown ceremonies, if only to remind Americans of the key military role played by (pre-revolutionary) France in helping the United States gain its independence -- toujours la grandeur .

Not only will French be sending troops, warships and marching bands to take part in the four-day festivities this October, Denis Collins reported in yesterday's Post, but President Francois Mitterrand has also indicated that he may attend. ("Yorktown, 1781-1981" and entwind French and American flags now decorate French Embassy mailing envelopes.) President Reagan will be there. But thus far, official Britain has rebuffed all offers to participate.

What we may have here is an Anglo-American confusion-across-the-ocean culture gap. Americans love historical anniversaries of national disasters in a way that our friends elsewhere in the world must find bizarre. Appropriately costumed and festooned, we run through an endless series of parades and pageants, musical events and mock battles in a ritual of remembrance that blurs ancient enmities and diffuses moral outrage. On the 25th anniversary of the Japanese attack on Pearl Harbor (once FDR's "day of infamy"), for example, groups of Japanese and Americans met to swap tales of a now-shared event that had once been considered the worst military humiliation in American history. It is not very clear what plans will emerge for the 150th anniversary of the Alamo, due in 1986, but it would surprise few people in this country if the ancestors of the defeated Texans invited the whole Mexican government to San Antonio for the occasion.

But the British do not seem to have much appetite for this, at least not in the case of Yorktown, despite the two centuries that separate the ministries of Lord North and Mrs. Thatcher. This is too bad, because if nothing else, the event would provide an unparalleled opportunity to promote British toursim before a vast audience of American Anglophiles. To portray the luckless Lord Cornwallis, why not send over Robert Morley, appropriately bewigged and singing, "We'll do anything for you, " while leading a contingent of 7,500 British travel agents. The Queen, if she chose to come, could use the occasion to offer her errant former American subjects a final opportunity to rejoin the Mother Country: "Ask yourself, are you really better off today than you were 200 years ago?"

Ever wanting to be part of the solution, as they say, we offer this sensible way out: why not make British participation in the Yorktown revelries contingent on a rip-snorting 175th anniversary celebration of the War of 1812 six years hence. No burning of Washington would be either authentic or complete, after all, if the British chose to abstain or, God forbid, took their business elsewhere.