NVQ's or Diplpma's as they are now called are vocational qualifications that you do 'on the job'. You are assessed for the qualification by being 'observed' doing the job.
If you are doing 8 hours with the children, then you will be observed against a set of standards (that the assessor will take you through). You would then have a conversation and be asked questions about what you have been doing. You will then be set a number of tasks to do before your next meeting with the assessor.
For example, if one of the standards is about differentiating a lesson for different ability levels, you may want to research what that means (ask a teacher), get some examples, plan a simple lesson that shows how you would differentiate. The assessor would then watch you do the lesson and give you feedback. (this example may be a bit OTT, but the only one I could think of).
You may find, that for funding purposes, you actually have to do a number of qualifications (called an apprenticeship framework), which would consist of the Diploma, maths, English and a technical certificate.
You don't need to go to college, as an assessor can come to school, but some places still do some of the qualifications at college.