Even if you do not require a visa, you must still satisfy the UKBA authorities at the port of entry that you meet the admission requirements, at the time when you arrive in the UK. There is no guaranteed right of entry whether you have a visa or not. It is ultimately up to the UKBA authorities at the port of entry to decide. There are a number of documents you must take with you in any case, in your hand luggage, such as your return flight ticket, evidence of funding, letters from sponsors or business you are visiting, or school you will study at. Full details are on the websites.