Brunei's currency is the Bruneian dollar, which is divided into 100 cents; you'll see it written as B$, or simply as $. The Bruneian dollar has parity with the Singapore dollar and both are legal tender in either country. Notes come in $1, $5, $10, $50, $100, $500, $1000 and $10,000 denominations; coins come in denominations of 1, 5, 10, 20 and 50 cents. The current exchange rate is B$3 to the pound or B$4.50 to the US dollar. There are two Malaysian ringgit to one Bruneian dollar.
Sterling and US dollar travellers' cheques can be cashed at banks, licensed moneychangers and some hotels. Major credit cards are accepted in most hotels and large shops. Banks will advance cash against major credit cards, and with American Express, Visa and Mastercard, you can withdraw money from automatic teller machines (ATMs). You can get money wired to you via any of the major banks in the capital.
There's only one budget place to stay in the capital and if you can't get in there, you're looking at around £20/US$30 minimum per night in a hotel, which means an average daily budget in Brunei is likely to start at around £25-30/US$37-45.