Firstly, the receiver unit was correctly receiving packets for a while and would then stop receiving altogether or have large gaps where no packets were received. Then there were periods when the message kept failing the CRC error checks over and over. Despite the fact the units are only about a metre apart, I would expect perfect packets with minimal error and yet this is not the case.
I can only presume there is some kind of weird interference where I am testing. I did try to reduce the baud rate but when I attempt to use the RF12_control() command to set the baud rate I am getting compile errors. Some kind of issue with the RFM12 driver and Arduino 1.5.8
Overall it has been very frustrating.