Two theories on how the TOCs have managed to lever your price increase up to 9%
a) by making use of the fact that the AVERAGE percentage increase is the figure that is regulated i.e. the TOC reduces the price of say Dover to Buggleskelly ( which no-one uses ) and at the same time increases Dover to London, which is uses by loads of people by MORE than the average figure.
This is what happened in Jan 2008 - the average % was 4.8% ( rpi + 1% ) but some season tickets went up by as much as 9.6%
b) if the said season ticket is 1st class, by increasing the multiplier relative to 2nd class.
Only 2nd class seasons are regulated.
This is exactly what Arriva XC did in May 2008 when they changed the multiplier from 1.5 to 1.7 and inflicted a 13% increase overnight.
It would be most interesting to find out if the increase was in Sep 2008 - more ammunition for those who are looking for evidence of "back-door" rises under the cover of simplification.
Put the details of where your ticket is from & to and i am sure that someone will be able to give more details of how, when and possibly why !