Cheers Matto, I thought I might be grasping at straws with my phone, it has never been as effective as the one I had on my Golf + and I'm now wondering if fitting LED's to my interior center light is causing a problem as I just read that having that on switches off the auto dimming. Maybe there's a slight current drain through them even with the light off. I'll go and pull the LED's out and see if that makes a difference.
Cheers,
Robert