Hi John thanks for that,
That's extra info that's very useful. I think I'll go ahead now and get some. I'll post progress, especially if I get into trouble 
I also joined this forum and got some useful stuff.
http://forum.jeelabs.net/forum
Cheers
Edit: I didn't immediately think to look at the Radio datasheet separately, but I found links and, as you said, it gives me the features I need.
http://www.sunrom.com/files/RFM12B.pdf and http://www.hoperf.com/upload/rf/RF12B.pdf
..features
Wakeup timer
• 2.2V – 3.8V power supply
• Low power consumption
• Standby current less than 0.3uA
0.3uA is low enough for me!