I'm on a budget and a very tight schedule and I need to get from the cruise pier in Southampton to the Southampton bus terminal to catch the Nat'l Express coach to Heathrow. Is it within walking distance or would I have to take a cab? If a cab is needed, are they readily available at the dock? Also, how long does it generally take to get from the dock to the bus station? I need to make reservations and am not sure which one to catch. Thanks!