Despite my issue upgrading to 2.5.2.3, I carried out an auto-centre with 2.5.2.1 and all worked well!
This is no help I realise Gunny 
I am using 2.14.16 10U beta firmware. I'll post SGP logs tomorrow.
With my fuss over the new SGP beta I forgot to switch on the 10U logs (doh!). I have a clear sky forecast tomorrow so will try again tomorrow.
Barry