Moving songs purchased on iPhone onto G5 iTunes

Hello there... Happy New Year!

I hope somebody can help me here.

I have a G5 running iTunes 8, and recently got an 8gig iPhone with iTunes on it, and I also have an iPod nano that my wife uses. I have one iTunes account that I purchase my music on.

My wife and I play in a covers band and when I'm at work I've gotten into the habit of thinking of a song that would be great for us to play, so I'll preview and download it onto my iPhone (via WiFi), thinking that I'll be able to move the songs onto the iTunes library on the G5 at home so she can move them onto her iPod, then we can familiarize ourselves with the music... but i can't!???

I just can't get the songs from my iPhone into the G5 iTunes library, which is set up with the same account. In iTunes (on the G5) I've got the iPhone set as 'Manually manage music and videos', but whenever I click 'sync' it warns me that the music will be deleted from my iPhone and replaced with the music from the G5 library (make sense?), so i don't go any further.

I've had the work-flow problem before, and the solution (out of pure frustration) was to re-purchase a load of songs just to get them onto the G5... which, i'm sure you'll agree, is completely ridiculous.

Am i missing something, or is Apple/iTunes SOOOOO lacking in foresight that they won't allow people to move music from an iPhone to a G5, even if it is authorised to do so, and running the exact same iTunes account?

To summarize, i want to move songs purchased on my iPhone into the G5 then take those songs into the iPod nano.

I hope somebody can help me, as i really don't want to have to re-purchase another load of music just to get this simple predicament sorted out.

Many thanks in advance.

James.