Some cricketers just don't seem to be able to take their county form into the Test arena. Crawley's still got age on his side so he could yet get better (although I note his first class batting average is surprisingly low at just over 30), but 2 players from years gone by who always spring to mind and really should've done better for England are Graeme Hick and Mark Ramprakash. Hick's first-class batting average was an impressive 52.23 but in test matches it was only 31.32. Ramprakash's first-class batting average was even better at 53.14, yet his test match batting average was a woeful 27.32. I think anyone averaging over 50 in first-class cricket should be more than capable of averaging over 40 in test cricket so both those players massively underperformed in test matches IMO.
Crawley in the England side for me is better than Ramprakash hick though in this set up would be an unbelievable player..