When the car got an MOT in 2011, it failed on the ball joint, but then the car MOT was passed (I assumed it had been fixed).
Ok, ball joint failed or failing, assume replaced if a proper fail and not an advisory
I looked at the MOT the car just had in August 2012, and it failed on the same thing at 5pm, with a note saying the car is dangerous to drive. But the car then passed it's MOT the following day at about 3pm... does this sound a bit iffy?
So another ball joint fail one year later. Not everybody replaces them in pairs, so this could be the other side?. The fail at 5pm suggests end of day and part ordered for next day. Job done at 3pm
The garage I bought the car from did a new MOT on October 4th, so that I had a years MOT, and it passed, with no advisories or anything.
You can MOT a car any time, but can only take advantages of the 1 month "extension" within the last month of the MOT. So your new MOT is exactly 12 months to Oct 3rd 2013. Present your car within a month of this for the new one to be consecutive (and allow plenty of time for fixing any fails in the last month while keeping the existing MOT legal)
I don't see a problem. Have you checked the full history on motinfo