2915 Connecticut Ave. NW. 332-8300. Pricing policy is in the process of change. L daily ex Sat, Sun. D daily. AE, DC, MC, V. Res sugg. Free parking in rear. Full bar.

Waiters and waitresses in very British vests and ties, a museum of royal abdication memorabilia and a small but enticingly original menu--at a reasonable $15 for three courses at dinner--have combined to inspire Mrs. Simpson's neighbors to dress up as if for downtown, but to stay uptown for dinner. The small restaurant is clearly elegant, and service has improved to a high polish. Unfortunately those delicious- sounding dishes turn out to be merely all right. They are fresh ingredients, yes, but cluttered with excess herbs or other garnishes and flavorings: fresh fish smothered in butter and nuts, grilled duck littered with gritty dried herbs, fried ravioli with ammoniac blue cheese sauce that drowns the bland cheese filling. Mrs. Simpson's kitchen is full of good ideas that seem carried out for effect rather than for their actual taste. Desserts, though, are exceptionally good, whether the lightest and lemoniest of mousses, the deepest and darkest of chocolate layer cakes or the mellowest of prunes marinated in spice and wine.