The installation was succesful and after doing a factory reset and clearing cache the phone booted up ok. It connected to my network provider for several seconds and then disconnected.
After several attempts at this process using different files, I noticed that the IMEI of my phone was no longer correct. At this point I thought I had bricked my phone by somehow corrupting the IMEI.
In an attempt to put it right, I reloaded Jelly Bean 4.1.2 and my phone now works fine again. Please can someone advise what I am doing wrong with this process and why the IMEI gets corrupted as this is obviously why the network rejects my phone when I install ICS.