A few days ago I remembered that my university library subscribes to the Naxos Music Library online. Basically, I can log on to the library website from off-campus, and listen to any Naxos CD I want in streaming audio. Right now I'm listening to the Bach Collegium Japan sing cantatas. I'm so going to use this during my exam.
(They also have a funny section for students studying music for GCSEs and A-levels.)
If you have a university affiliation, you too may be able to access this!