Hi Anni
I don't have a clue about the test, I only mentioned the numeracy and literacy as they are the ones which NVQ candidates have to take if their qualification is government funded and they haven't current got English and Maths GCSE grade a - c (I think).
As you already work in the council, is there someone you know who can give you a hint about the test? For my last interview, I was asked to deliver a micro-teach for new NVQ candidates.
As for the struggling candidate, make sure you have a good rapport, highlight the positives in the evidence they have provided and show then how they could have gained even more from it. Make sure your visits are frequent enough, I visit every two weeks as this keeps the momentum and motivation going. Ask about work and home, is he/she getting enough time to produce he work? Are you asking for too much to be completed? Does the candidate understand what the standards are asking for?
I usually find a struggling candidate is one that hasn't yet understood the process and how the standards are laid out and what they are asking for. Quality time invested in getting the message across will pay dividends. NEVER tell a candidate that their evidence is insufficient without saying EXACTLY how it needs to be altered/edited.
I ramble on.

Dave