BUTTERFIELD's Indian Railway Tours (0262 470230) has space available for its 23- day Pakistan railway tour departing 12 March. Travellers are accommodated in a four- berth cabin on an air-conditioned sleeper coach attached to a private dining car. 'Flexibility, tolerance and a genuine interest in different cultures to our own are vital to the visitor's enjoyment of this fascinating land,' says the guide. The holiday costs pounds 1,450, including a return London-Karachi flight.