I have multiple WAV files which I want to change the BPM for but I don't want to convert them to anything. Will I be able to keep the files as WAVs after I've changed the BPM?
Yes, you can do this without changing the file format. Download and install Audacity (it's a free audio editor). Load the WAV file and then go to Effects > Change tempo. Insert the new BPM, and you'll see the results after the file has been processed. You can change BPM for a section of the file or for the entire track.
Download Audacity: http://audacityteam.org/download/
That's great, can i just confirm that it wont change the pitch as i want that to remain the same?