(18 Mar 2017, 3:15 pm)Dan wrote Not sure which one Stand H is, but the X21 service stops at the Metrocentre Coach Park... It doesn't go into the Metrocentre Interchange, as far as I know.
I believe stand H is the stand the X22, X24 and X88 currently leave from.
You are quite right, the X21 does not use the bus station at all and instead uses the stop in the coach park, as this picture demonstrates: https://flic.kr/p/JrTNNX
For some reason, some of the online timetables seem to incorrectly state that the X21 leaves from stand H in the bus station, rather than the coach park. No idea why this is though?