An investor can profit from the difference between two interest rates in two different economies by buying the currency with the higher interest rate and shorting the currency with the lower interest rate. Prior to the 2008 financial crisis, it was very common to short the Japanese yen (JPY) and buy British pounds (GBP) because the interest rate differential was very large. This strategy is sometimes referred to as a "carry trade."
Most retail investors should spend time investigating a forex dealer to find out whether it is regulated in the U.S. or the U.K. (dealers in the U.S. and U.K. have more oversight) or in a country with lax rules and oversight. It is also a good idea to find out what kind of account protections are available in case of a market crisis, or if a dealer becomes insolvent.