The _proposed_ NPPL medical standards are aligned with driver ones. Class 2 driver would be reqired for "full" NPPL privileges, e.g. passenger carrying (up to 3). For those who don't qualify for Class 2 driver, normal driver medical standards would allow flying solo.
There are significant differences between Class 2 driver and Class 2 aviation, best bet is to compare the CAA and DVLA websites.
Pilots are always responsible for certifying their own fitness to fly, and I believe that NPPL medicals would involve an _endorsement_ of that certification at the time of examination - but I'm not a doctor or a lawyer!