I think you'll be fine, a teacher is a teacher at the end of the day and if ur parents are doing a good job. I had a teacher for a few months, he was shockingly awful, and after that I just learnt with my dad and ended up passing. it's more about confidence and familiarisation with driving than perfection. one thing I did Do which was super helpful was getting a good instructor recommendation from a friend and doing one mock test with him a few days before my test. if you're local to Worcestershire, I can give you his details! good luck x