Something To Declare: all change for Heathrow; Hong Kong; Marrakesh

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Warning of the week: all change for Heathrow

The most expensive railway in the world is the Heathrow Express between London Paddington and Britain's busiest airport; the one-way fare is £13, or a couple of pounds more if you buy your ticket on board.

Many travellers prefer to use the slower but much cheaper Underground (fare £3.80 from anywhere in central London). But for today, tomorrow and the next two weekends, journeys will be much trickier and slower. Piccadilly Line trains will terminate at Northfields, where a bus will take over, calling at all stations to Heathrow.

Passengers for the airport should get off at Acton Town, from which non-stop bus services will run to the central area (for Terminals 1, 2 and 3) and Terminal 4. For anyone with substantial luggage, this will be a cumbersome transfer, and every traveller can expect a longer journey.

On 28 March, the world's busiest airport in terms of international flights is about to get more confusing - at least for passengers on British Airways. The second phase of BA's flight-switch programme takes place on that day, to coincide with the start of the summer schedules.

The airline wants to free up space at its main Terminals, 1 and 4, at key times, and facilitate transfers between short- and long-haul flights.

Traditionally, short-haul flights have used Terminal 1, but services to Brussels, Copenhagen, Geneva, Lyon, Oslo, Vienna and Zurich are to switch to Terminal 4. On the same day, Athens flights move back to Terminal 1, along with links with Hong Kong, Moscow, Los Angeles and San Francisco.

Bargain of the week: Hong Kong

When the first cheap flights were sold between London and Hong Kong in the early Eighties, the lowest fare was a standby flight at £198 return. This represented about two weeks' work at the average national wage. Twenty years later, the journey is far faster and more comfortable, yet the price has risen only to £299 return - three days' labour for the typical UK worker - flying on British Airways (0870 850 9 850, www.ba.com) with a departure in February or March.

Flights are filling fast, and will continue to do so until the offer ends at 10pm on Tuesday 27 January, but if you are flexible about dates and times you should find some seats available at this low fare.

If you want to travel to Hong Kong later in the year, and can travel with a partner, consider the deal being sold by Airline Network (0870 241 0052, www.airlinenetwork.co.uk).

The agency is selling a companion fare on Cathay Pacific, also from Heathrow, for return flights and three nights in a three-star hotel from £379. The price per person is based on two people travelling and is available for departures from 1 February to 17 June, although not between 21 March and 25 April. It is also valid for November.

For travel from other UK airports, the deals do not look so impressive; through discount agents, fares from most cities via Amsterdam or Paris on KLM or Air France are around the £400 mark.

Destination of the week: Marrakesh

The memories of last May's terrorist attack in Casablanca, in which 45 people died, continues to depress the market between the UK and Morocco. Consequently, planes and hotels have plenty of space at good fares. Tapestry Holidays (020-8235 7700, www.tapestryholidays.com) has launched a flexible range of trips, staying in small and mostly traditional hotels in Morocco's finest city.

Prices are typically below £500 for a three-night stay - though if you insist on staying at La Mamounia, the lowest price of £500 applies only from 21 June to 7 July. These rates include scheduled flights from Gatwick on Royal Air Maroc. A 15 per cent discount is available if you book before the end of February.

The Foreign Office says: "Although the Moroccan authorities have arrested and imprisoned a number of those considered to be responsible for the attacks, there is a continuing risk of further attacks. Maintain a high level of vigilance in public places such as hotels and shopping areas."