Turns out this was caused by having the external GSP antenna plugged in.
In a bit of a 180 turn of events I'm actually going to be selling this unit. Have decided to do a full system upgrade with a higher end head unit, speakers, amp etc so I'll be look to sell this unit over the next few weeks.
Has nothing to do with this unit, its been great and the after care service has actually been up there with the best I've received (spoken with them a few time around issue of my making).
So if anyone is on the fence and wants to try on the cheap. Ping me and we can sort something out (or ill stick up a for sale ad).