Radio Advert Recording

I wrote a script for the Radio advert which we then recorded using a microphone linked directly with Garage Band on the iMac. One major problem we stumbled upon is the fact that the microphone only records Mono which means that the recording will come out from only one speaker (in our case it turns out that only the left speaker has any sound).
When Playing this through the earphones the left ear is clear and you can hear all of the voice-over whereas the right ear has little sound and adds an unwanted echoing to the recording.
We recorded with me, and trialled three other people before coming to the conclusion that my voice was the clearest and that it made sense if the narrator of the documentary itself is the same person as the advert voice-over however this doesn't have to be the case.

We also had people walking into the room and talking which prolonged the number of takes and time it took to record the Radio Advert, as we were recording in a school, it isn't ideal but it's something we must endure and overlook.