Is O'CONOR DON, 88 Marylebone Lane, W1 (020 7935 9311) the best Irish pub in London? You can stand at the marble bar counter and watch them slowly, lovingly pour the Guinness, or if you sit down they'll bring your drink to your table and grand Irish food as well. A dozen Irish oysters and a pint of the good stuff and you'll be ready for whatever Marylebone has in mind for you.