My nearest garage is BP and I did use their ultimate until I tried Shell V Power from a garage 8 miles from me. The difference was noticeable, car felt more responsive and fuel economy went up as well.
Since then I work my refills around being near the Shell garage and haven’t used BP since.
V Power whenever possible, Tesco Momentum is next best but there are several threads on other sites saying Tesco is very good but some locations dont sell it quickly and therefore its not always at 99 Ron as the additives have a shelf life.
I have always used this in big towns and never found a problem.
I have also had ot use JET Super Unleaded (97 Ron) on track days when there is nothing else availiable in the area and been very happy with the performance but V Power is what the car was mapped to run on so that is what I use in the main.
I have used Tesco momentum in all of my cars for probably the last 10 years. I never noticed any differences in knock values between Momentum and Vpower on any of the cars. Its just easier on the pocket than V power.