FARES to a range of cities in India have fallen. The national carrier, Air India, has introduced a flat fare from Heathrow to all its international and domestic destinations, from Trivandrum to Amritsar, for pounds 435. Tickets are available only from travel agents and are being supplied through Welcome Travel (071-439 3627). In response, the Sri Lankan airline Air Lanka has cut its fares to southern India (via Colombo). Flights from Heathrow to Trivandrum and Madras are available from The Travel Bug (071-835 2000) for pounds 432, for departures up to the end of November.