Mri says no significant intracranial abnormality, but, occasional foci of white matter hyperintensity are nonspecific. what does this mean/ signify? should i ignore this or see a specialist? gp is invalidating and not helpful?

Appears that MRI is reassuring. Would not be concerned with nonspecific white matter lesions, which could be due to smoking, migraine, prior head injuries, and multiple other causes. Since you have concerns, meet with the radiologist and discuss this further. If you are dissatisfied with your GP, meet at that office and discuss your frustrations.