In reply to Lynsety:
It sounds like you have a sticky piston - quite common, and usually fixed by a re bleed and a good clean up around the piston.
As Toby A says, ideally you don't want to pull your levers without the disc in, as this can lead tot the pistons popping out. Its not disastrous with most makes, but will need to be popped back in and re bled.
In terms of your levers going back to the bar, it sounds like you need a re bleed anyway.
How long is it since you changed the oil/fluid?