Try this if You have good strong breath.
Connect a garden hose fitting the one that's push fit with circlip on to an 18inch length of garden hose then connect it to the basin cold tap. Turn the cold tap on and blow hard down the pipe and with luck you will blow the airlocked water out of the fee pipe that should kick it all into gear to flow without airlocking it up. I've done it that way the only other way is same fitting but using kitchen mains tap to get the pressure to push the airlocked water out, of course you will need someone keeping an eye on the basin end to make sure the pipe doesn't come off.
Hope it helps. I'm glad if this is too late it means you've done it.
Nobby
November 2008