LONDON.- Art collector Charles Saatchi has a gift for Britain. It includes Tracy Emin’s messy bed, Grayson Perry’s explicit pottery and a room full of engine oil. The advertising tycoon, whose patronage made household names of artists like Emin and Damien Hirst, announced Thursday he is donating his London gallery and 200 works in its collection to the nation as a new public art museum. The gallery said the works, valued at more than 25 million pounds ($37 million), will be given to the government. The 70,000-square foot (6,500-square meter) Saatchi Gallery will be renamed the Museum of Contemporary Art, London. The artworks being donated include Emin’s “My Bed” — the artist’s famous recreation of her boudoir, complete with empty liquor bottles, condoms and cigarette butts — and Richard Wilson’s “20:50,” an eye-dazzling room filled with oil. There are also works by Perry — best known for vases adorned with disturbing twists on classical scenes — and artists f