In reply to cisco:
From the end of the M56 to Manchester centre it would normally take about 30 mins but Monday morning is probably the slowest day of the week. Bear in mind the traffic can often start backing up a few junctions before that, nos. 6 or 7 and you can often get held up by traffic queueing for the Stockport turn off which makes it look like there's some trouble ahead but as soon as you're past there it speeds up again.
I've usually found getting in the outside lane to get past the Stockport turn off and the inside lane at the start of the Princess Parkway to be the best bet!