How are you receiving Freeview?
Al Jazeera is available on UHF but only on Sky via satellite.
You can also watch live online
Not all broadcasters can fulfil the task to broadcast their channel on Satellite and Terrestrial, hopefully sometime in the future Al Jazeera can do this.
Did you know that Whanganui can receive Freeview HD (via an UHF Aerial) which has the Al Jazeera channel? You could probably swap services and get even more for free. '