I couldn't be bothered reading the whole thread so if this was said then sorry. In my knowledge BP are consitant with their fuels in that when they say the fuel is 98ron than it is 98ron as opposed to shell which are inconsistent. There have been reports where the advertised shell v power racing which is supposed to have 100ron and actually have mixed results ranging from 95-102ron. These reports were made due to the necessity of high powered cars needing to run on high octane fuel, and when one of the cars exhibited detonation they traced it back to the fuel, thus conducting tests on different fuels. The article is somewhere on the net if you can find it. So definantly BP ultimate, i've personally never really liked shell anyways, my second choice is caltex.

Another source of information was the BP are the only fuel company which has a true 98 octane percentage in their fuels and that the others all require additives to reach their 98 octane which could explain for the variance in fuel octane ratings found in other fuels.