In the roof rafters is fine. As long as the roof is not made of steel or slate. Steel attenuates 80% of the signal, slate about 50%. Everything else is invisible to radio frequency waves at around 100MHz
That's brilliant Chris, - now there'll be nothing visible externally. >>
Next thing is to figure out is where to obtain an appropriate splitter box (RF?) - as would like to share the FM dipole amongst the lounge and bedroom stereo systems.