NPPL _proposed_ medical classes are as for driving. N.B. nothing in legislation yet!
Group 1 (normal driving standards) should allow for solo flying (no passengers).
Group 2 (professional driving) should allow up to 3 passengers - but that would require 10 years without seizures or medication.
There is info on the Flyer website, and detailed standards for driving on the DVLA website.
Hope that helps!