(b) keep the original registration when it is obviously not the original car.
Restoration is a different issue. But then most restoration projects (that I have seen or been aware of) use mostly original parts. Therefore would be OK to keep the original reg. However, I believe that once it is restored, a vehicle should again have to undergo some sort of test as well.
So far as B goes H.
I, personally have no problem with a Q plate if that is what it takes, my problem is with a Q plate and requiring SVA which is a totally inappropriate test, because it would be impossible to pass with anything built before 1998 because nothing that early is designed to get through.
Side repeaters, fold back mirrors, etc.
The restoration issue is even more complicated, see my previous post about a Lotus Elan. The new chassis and engine would improve the car and make it safer, but it would not pass SVA, therefore it would never hit the road..
And what happens when the supply of NOS parts dry up?
Remanufactured parts make the Identity of the car suspect and therefore the risk of SVA comes up again.
This is not the time to bury your head in the sand and say "Everything should be tested", Everything is tested, It's called the MOT.
But this is a test that pre 1998 stuff cannot pass, therefore it will never get to an MOT.
I'll accept an Engineer's report on my Zodiac any day, Done by someone who knows what he's looking at and can tell the difference between a well enginered car that is built to RACMSA specs, which allows it to run 13 seconds on the strip, and a car that doesn't have fold back mirrors, side repeaters and nicely shaped headlamp dip switches.