OK you would be about 14 1/2 miles from the NEC at that coach station. That equates to about 1/2 hour driving.
An 11 min walk to New Street station, train to Birm Int'l and 20 walk to the NEC would work out around 45 mins.
I assume you are going Mon/Tues for the CRS?
Edit: A typical taxi fare between The airport and the city centre is about £20 each way