If it’s obstructing your right-of-way, (scratching the car would be an obstruction) and he will not allow you to cut it, if you do cut it, he can alleged criminal damage.
Your remedy is to get a solicitor to write to him telling him that unless he either cuts the hedge himself or allows you to cut it, you will apply to court for an injunction, at your discretion, to either allow you to cut it or make him cut it and that in addition to the application for the injunction, you will asked the court to award the solicitors and court costs against him.
I suggest that in the letter, the solicitor gives a timescale of 1 week and if it doesn’t happen after one week, then you have no alternative but to make the court application.
Can I clarify anything for you?
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We can still exchange emails. Best wishes.