yes, i thought that might be the case...
I used Ultimate for months and then for the last few tanks I have used Optimax. So far the Optimax seems to be slightly better in tems of pinging (still need to sort that out though) and fuel consumption.
My average L/100klms was going up with Ultimate and has started to come down now that I am using Optimax, I haven't changed my driving style.
I will just have to find whats best for my car, out of the available fuels.
Thanks for your help.