It takes between 1:20 (Manchester Piccadilly to Blackpool North) and 1:45 (Blackpool South).
50 minutes
According to Google Maps using Public Transport, it will take 4hrs 14 mins to 4 hrs 23 mins. It will also cost you around £45.66.
From Birmingham New St to Blackpool North it takes 2.5 hours by train, with 1 change in Preston.
couple of hours (3?) if you take the high speed to st pancras