Most shops are open Monday-Saturday until 7 pm, although shops in busy shopping or tourist areas are likely to be open on Sunday as well. Very few stores close for lunch 1-2 pm, but it's often difficult to contact anyone in an office at that time. In London, business meetings tend to be fairly relaxed, though some bastions of tradition are still stiffly formal. Shake hands upon meeting, but hold off on exchanging business cards until later. An informal drink is also quite common after the close of the business day.
Business conventions call for a suit and tie or their female counterpart.
If you're isiting a conservative company, the more traditional the cut and color, the better. The most expensive restaurants and upscale hotel dining rooms expect patrons to dress appropriately. Always ask if service was added whenever you are uncertain. Londoners ask for the optional service charge to be removed or reduced in the event of truly bad or overtly rude service. Usherettes are not tipped.