Nationals of a select few countries can visit Mongolia visa-free for a specified period of time. The duration the visa is valid for will depend on your nationality and can range from 14 to 90 days. Unfortunately, visa-free entry into Mongolia is not available for UK citizens at this time.
Mongolia visa-free countries for ordinary passport holders*:
USA, Malaysia, Israel, Cuba, Philippines, Singapore, Hong Kong, Macao, Kazakhstan, Azerbaijan, Turkmenistan, Ukraine, Georgia, Belarus, Kirgizstan, Moldavia, Tajikistan, Laos.
*Official and diplomatic passport holders from China, Russia, Turkey and India may also qualify for visa-free entry to Mongolia.