Apparently I have been made an O2 Select member.
I am not sure what the requirement is to become a 'special' priority member, but I am guessing 7-8 years on O2 may have helped! Among the "benefits" of being one of their top customers, I get priority customer service over a freephone number - which may have been useful a couple of years ago when I had to call them up loads of times due to billing issues (my complaints documented on this very blog, look it up as I can't be bothered).
I also get to upgrade 3 months before the end of my contract (or credit to account). Replacement mobile phones are also promised to be made available to me within 24 hours if I have a problem with my phone during its warranty period. Some has complained that we are required to pay an 'excess fee', but I don't see that written in their short T&C. Finally I also get 25% off all accessories sold at their stores. O2 stores tend to mark up the prices of their stuffs, so I doubt I'll be taking advantage of their generous offer anytime soon (unless they start selling Denons!).