Well, I emailed Mikal Hart (reverse geocache inventor) with my plea and he replied back last night with a simple fix - remove the ';' at the end of my while statement. Guess what, a nice flood of serial data.. Such a simple fix, I just wasn't familiar with the language

Thank you so much Paul for all your troubleshooting help, I wouldn't have managed to resolve all this without your troubleshooting..
And thanks too wayneft for chipping in. I can safely say too that yep, this chip definitely works with 5V, so all is good there..
I'll write the project up and post back within a week or two with the full build log

might just squeeze it in with a fraction of time to spare now

Cheers,
Dan