After reading initial comments, I though it would be best not to be too hasty and make such a rash decision, although granted such a mistake should never have been made.
Although after reading how much you are having to pay, 100% I believe you should be looking for another tutor, especially considering you mentioned mistakes have occurred on various occasions.
I know it's been mentioned that perhaps £60+ in certain areas isn't uncommon, but I still believe that's a comparatively extortionate price.
There should be many qualified tutors available that wouldn't make such careless mistakes and charge less of a premium for providing an arguably better service.
This is your money and your education, so it's your call.