Thanks Henrik.

There is SO MUCH in the datasheet for this device!
Just when you think you have everything under control, something else raises its ugly head

I will try your configs and recommended changes over the next 24-48 hours and report back - hopefully with good news.

I went out this afternoon and bought a couple of crystals to play with - just in case. I now have 4, 8 and 20Mhz crystals to plug in, if and when required.

Cheers
Barry
VK2XBP