A grommet performs the same task as the Eustachian Tube, i.e. allows pressure to equalise between the outer ear and middle ear.
Not trying to be facetious, but the fact that grommets are even mentioned in a discussion relating to a completely different part of the ear is indicative of how tricky such issues are to diagnose effectively. I have been told by ENT pro's that they believe many people are fitted with grommets totally unnecessarily... In my own case, numerous GPs said I needed them, yet I have no problems flying and now know my issues are something totally different.
Vestibular Neuritis also has similar symptoms to a Vestibular Migraine - try a Google on that. Confused? Join the club...
Regardless of exact diagnosis, anyone with the symptoms discussed here will be guaranteed to benefit from 3 protocols:
Total cessation of alcohol (alcohol affects the comparative balance of fluid in the inner ear - hence balance issues when you get drunk )
No caffeine
Regular, vigorous aerobic exercise.
Do all 3 of the above and I doubt you'll be cured, but I'll eat my hat if you don't see an obvious improvement.