It is important to make this initial appointment as early as possible - at least 6 weeks before you travel - as a second appointment will be required with the practice nurse to actually receive the vaccinations. These vaccines have to be ordered as they are not a stock vaccine. Your second appointment needs to be at least 2 weeks before you travel to allow the vaccines to work.
Some travel vaccines are ordered on a private prescription and these incur a charge over and above the normal prescription charge. This is because not all travel vaccinations are included in the services provided by the NHS.