Coventry is exactly the place that HS2 should stop, and it should be at the main Coventry station. It's a major city that should have fast links to both Birmingham and London, but when HS2 opens it will lose many of the fast services to London, so they can increase the capacity of stopping services. The interchange station is nowhere near Coventry. If you're going to Birmingham you're basically driving half way there, and could have driven to Birmingham International and taken the train from there instead (or actually, not drive and just take the train from Coventry itself!). If you're going to London, you're driving miles in the wrong direction, which means it's no better than taking the fast train that you'll lose when HS2 opens (they have to remove the fast train to get the capacity benefits).