Transport/amount of time in Manchester?

To be able to fly-out to Barcelona I'll be coming in Heathrow, London and will need certainly to get a taxi to Gatwick. Just how long can this get? Approximately? Can there be something I ought to keep a heads-up for?

Very first time available, traveling solo.

you consider the National Express coach in the Main Bus Station at Heathrow, that will be near devices 1,2,3... In the event that you come right into final four or five get the shuttle bus for the Bus Stop...

Source : http://www.londontowncarhire.co.uk/