Interview Transcription

I am conducting PhD research interviews that need transcribing. I expect to have around 13 hours of audio in total and would like a price per hour audio transcribed. The audio is in english and is non technical. Time stamping is not required, but I would like it accurate and spell checked otherwise. I have 3 hours recorded already and would like to feed the remainder through as and when recorded over the next month (mid May is my target completion date for this work, with transcribing to be finished by end May latest).

The recordings are mp3 format and can be supplied by internet or CD. There is nothing particulary sensitive in the content of the interviews, but I have promised my interviewees that I would have any transcribers sign a confidentiality document, so this will be a necessary before work can commence.
Thanks