Unlucky with your results. If it's any consolation I was in the same boat - got a borderline pass on one of the tests, not good enough for my TOC, 3 years ago. Retook the tests privately, (have to wait 6 months), failed one of those new style tests, took that again after waiting another 6 months, then had all tests in the bag, waited for my local depot to recruit again. Had to take interview again, passed that again, I'm now 1 week into my course.
The good news for you is its not a fail; and you will only need to retake that one test again, not any that you have previously passed, and it doesn't count towards one of your 2 'strikes'.
Also good is that the test results stand for quite a long time, it varies from TOCs but I have heard from 2-5 years mentioned.
You can retake the tests privately if you need - contact DBS in Donny though you will have to wait those 6 months. This 'may' help at sift stage of applications- the TOC knows they won't have to pay for your tests or find you a spot on test day. (You will never know if that had an effect though if you get an interview!)
Loads of Northern recruitment happening at Sheffield over the next year. Watch the Northern page every day after your six months. And I do mean every day. And don't trust the alerts.
Good luck