Sorry if I've missed something here, but something doesn't add up to me.
You said in your original post that although you don't have 2 years NCB right now, you will have by 1st September.
You then go on to say that you're not actually driving right now.
That infers you don't have a current insurance policy. You can only accrue a NCB through actually being insured. Unless the rules have changed, you have to have been insured for a full year before the year of NCB is accrued. Being insured for any less time than a year accrues nothing.
If there's a break in the policy before you reach a full year, even if you've done 11 months, those 11 months don't count. The only exception to this is 'gap insurance', whereby you're allowed to bridge the gap between two policies.
For example:
Normal insurance. You do 9 months on one policy, then end the policy. You have no car for a month, or however long, so you have no need for insurance. You then start a new policy. Your NCB will be the same as what it was at the start of the previous policy you did 9 months on. Those 9 months aren't counted, as you didn't complete a full year.
With gap insurance, those 9 months are counted. So you'll accrue another year of NCB in 3 months, rather than in 12 months.
