2 links have been added on this idea.
  1. There’s this, but yep, an app your uni recommends would allow all colleges and unis to offer the service to students. The costs of new books are silly tbh and you only use them once, if at all.

  2. Newcastle Uni has a programme for this, but there should be a site or app where you just list your course and it finds the cheapest version of each second-hand book you will need.