That great milandro , thank you. I was concerned it was a camera issue as Ive not had this before using canon for 10 years ,mind you I rarely take a sunset photgraph to be honest !
Now I know what its called there are some work arounds in Lightroom for me.
I got the x100 when the S was released and have used it a great deal and I have now traded in all canon (dslr and compact) and film cameras (2xRollies) for x-t20 a few weeks ago and I'm really looking forward to using it a lot more.
Some great info on these forums, I'm sure Ill be back on soon