One of my 'of choice' restaurants is Le Caprice, near Piccadilly, London. I find it a nice environment, and there are always a number of dishes on the menu that take my fancy. It has a nice blend - it's not too formal or overbearing, and it's where I tend to go when I'm eating on business in the capital.
Le Caprice has been around for donkey's years, and is a sister restaurant to The Ivy. I'm not adept at describing ambience and things, but it's a little like its famous sibling - I suppose you'd describe it as a modern take on a traditional restaurant. Of course, it's also quite popular, so you do need to book it a reasonable time in advance.
It has everything from light, simple food like a well-done fish and chips and a tasty Caesar salad, to duck confit and a good calf's liver. In other words, a lot of classic dishes, but done just right.