UK passport holders can travel to Brazil for stays up to 90 days in a 12-month period. You can extend this for a further 90 days and are granted by the Federal Police in Brazil. Your passport must be valid for a minimum period of 6 months from the date of entry into Brazil. Ensure that your passport is stamped on arrival, otherwise you could be fined on departure.
On arrival, you may be asked to present evidence of accommodation bookings, an outbound ticket and means to support themselves financially during their stay.