The Q plate thing....
Brfore the days of SVA, all kit cars which did not retain the original vehicle chassis (floorpan) got a Q registration.
Since SVA, you have the chance to get an age-related plate:
All new parts means you can get a current year registration.
Sufficient items off one donor car gets you a reg of the same year as the donor.
Too many items from different donors means you get a Q.
Note that re-constructed production cars (eg a good one made out of 2 or more damaged ones) also get a Q when re-registered, so this is where some of the anti-Q stigma stems from.
With a non-Q registration, you can do a cherished transfer of a number the same age or older than the donor, but no newer.
With a Q, you cannot transfer plates (at the moment) but there are plans to make "Cherished Q" plates available in the near future.
Hope this helps,
Simon