Pounds are the currency in 80 Days. You always start with £4000 and can earn more by trading goods, visiting the bank/begging, or winning games. You can lose pounds by losing games or being robbed.
The currency does not change ever in-game, regardless of if you're out of British jurisdiction (For example, British Pounds don't turn to American Dollars in America, nor do Pounds turn to Russian Rubles in the Russian Empire).