You can apply for your provisional car licence 3 months before you are 17 years old. You can only apply for a moped licence before this time. If you get certain disability living allowances you can apply for a car licence 3 months before your 16th birthday. The cost is £34 and best done online at Gov.UK
Knaresborough or Northallerton Test area? Neither one is an easy option. The pass rates are about the same for both. The standards of assessment are the same at both areas. Northallerton is also further away from the Ripon area so getting there and back will cost you much more in the long run.