Brits are slightly more formal in business matters than the Americans. This does not mean less friendly. In fact, Brits are very personable in business relationships.
You will find your new contacts even more helpful when they notice your genuine interest in getting to know their culture and appreciating their heritage. It would not be unusual to be invited to a client's home for dinner or for a night out on the town.
As with most new business relationships, it is good to adapt to the host country's culture. Brits tend to start new business relationships on a more formal footing—especially if you have never had any previous contact. The preference is that informality should be offered and not assumed.
The British are a little more liberal regarding mixing alcohol with business. Europeans in general have no stigma attached to the responsible use of alcohol. Many business meetings are held in public houses (pubs) across the country or over a meal and alcohol may be consumed. Again, it is best to follow the lead of your host and adapt accordingly.
The most common answer to this question is to avoid loud, aggressive behaviour as this is typically not very well received—unless for some reason it is expected in your line of business or the surroundings you are in. In fact you may find the British directness in response to such behaviour startling at first. Read more on this subject on our Culture Shock! page. Generally though, as with most cultures, it is always safe to adapt one's behaviour according to the industry expectation in the country you are visiting. If you have specific questions here or are concerned, we can help you with a more personalized answer.
This depends on your line of business. Overall, Americans tend to have a stronger propensity towards casual attire than Brits. This is particularly apparent during evening events and the more formal gatherings you may attend.