How do you turn off the automatic radio search on a Vauxhall Zafira?

I've just bought a Zafira Club (the basic, no frills model) and want to use my wireless radio transmitter with my I-Pod to listen to MP3s on the car radio.

But when I set the radio to an empty section of waveband to match up with the transmitter, I can't get the radio to stick there. Even when I save the band to one of thethe radio's memory slots, the radio will only stay there for a few seconds before the search function kicks-in and the band starts wanderuing up and down looking for a station. The Radio isn't broken, as it will stick to regular radio stations just fine, but it won't let me listen to my I-Pod via the transmitter. Deactivating the RDS (Radio Data System) doesn't help.

Does anyone know how to override the the auto station search on a Zafira radio?