El Supremo,
The highest that I have achieved (a few years ago now) is 11.7 which was considered to be a good score by my P.E teachers.
If it helps any, and bearing in mind I went through IOT in the 90s, our course was a 'guinnea pig' course for the PEdOs at Cosford. Consequently, everything we did fitness and test wise was always to max endeavour rather than a defined limit. On my fitness test about 2/3 of the way through the course I got to level 13-something which the PTIs viewed as being a passable effort for a 23 yr old.
Now as an ahem mid-30s (damn time goes fast), I did my most recent fitness test about 2 weeks back on return from theatre and got to level 11.3. Not bad for an old fart, and the last man standing in the gym amongst a bunch of wheezing 20-somethings.
Now fitness standards and test regimes have changed massively since I went through, however, the moral of the story is that whatever you think is good will never be good enough for the PTIs. As far as they are concerned an 'aircrew pass' i.e. scraping in, is not good enough - 'just enough is not enough' was one of our Sqn Cdr's favourite sayings. Basically, before you get to OASC / IOT, you would do well to maximise your CV capacity, getting it to as high a level as you can manage
I find interval training worked for me - it helped my cardio improve quite rapidly in a short space of time. On det, I did most of my running on a treadmill in the gym. By the time I left theatre I was starting with a 5 min warm-up at 11km/hr and then at the 5 min point ramping the speed up to 16.5km/hr for 1 min then dropping back to 11.5km/hr for 2 mins and so on, repeating for the next 30 mins. Try it - it's harder than you think, especially if you set yourself a goal of increasing the jog / run speeds by 0.5km/hr every couple of weeks. Assuming you are already reasonably fit, you should find your CV capacity increases quite quickly, but just be aware that you also need to do some long distance runs too; if all you do is the interval training you will find you train your body to do relatively short - mid distance runs very quickly but you will be screwed on the longer runs you do at IOT.