Citizens of United Kingdom can enter Belarus visa free for up to 30 Days. You only need to purchase a visa if you intend to travel to Belarus for longer than 30 Days.
British Citizens can visit Belarus visa free for 30 days when entering through the Minsk National Airport. You must be able to provide an ordinary passport, which must be valid for at least 90 days beyond the intended date of departure, sufficient funds of at least £20 per day of visit and medical insurance valid for the whole duration of the stay. This visa free regime does not apply to people arriving to Belarus by place from Russia and planning to go to the airports of Russia.
Visitors to Belarus are required to register at the local Citizenship and Migration Office of the Ministry of Interior of Belarus within 5 business days. There, the local police authorities will issue a registration stamp, which will be attached to your passport. If you are staying in a hotel, this should be arranged by the hotel services.