Hi, I'm arriving at Heathrow July 27 (early morning),is there a bus line from Heathrow that goes directly to Euston station? I'll be taking a train from there to Manchester. If so, do I need to make arrangements before hand or can I just buy a ticket once I go through customs? Thanks.

On London transit journey planner website, it does not show bus but the options of express train (faster) or tube (less expensive). Heathrow Express to Paddington Station and then Circle Line to Euston (about 45 minutes, express portion nice airconditioned train, 14 pounds 50 for train and 2 pounds for tube) or tube Picadilly line to Green Park Station and then Victoria Line to Euston (about 55 minutes, no airconditioning, at most 3 pounds 50). See http://journeyplanner.tfl.gov.uk. For either one you can purchase your ticket in the airport after you clear customs and immigration.

Perhaps if you had heard of a direct bus service it was this "Though many people seem unaware, the popular Heathrow to London Airbus service stopped running in late 2004 after 23 years of service. Airbus ran 3 routes, the A1, A2 and not surprisingly, the A3. The A1 terminated at Victoria but also made stops along the Cromwell Road which linked up with local hotels, bus and tube stops. The A2 stopped at Marble Arch and along Hyde Park and went onto to Kings Cross via the West End. The A3 was planned to link out to Stansted Airport. These buses were run by London United."

Wouldn't go into London to get a train to Manchester - especially early morning as at some point you'll have to fight it out with commuters

It's would be easier to take a bus service to Watford Junction then the train north but you can't collect pre-booked tickets at either Heathrow or Watford Junction, so I'd suggest taking the bus to Reading, pick up your tickets there and taje the train north. Means a chage of train but a lot less stress than going into London during rush hour