I've put my name down to exhibit at Scalford. If I get a room I will be taking my 682ZX and my Akai GX-77 R2R. Naks are stunning decks. I've not owned a Dragon or CR-7 but my 682ZX took a big leap in performance when I replaced the 4558 op-amps. Any 3-head Nak is a stunning recorder, same for any of the "Classic" transport machines. I am currently working on a 482 and a 482Z, and will be adding some modern "Super" regulators to them for the audio sections.
I understand the Dragon has C-mos switches in the signal path that are easily replaced by better ones.
Just about any Nak will make a better recording on a TDK-D or Maxell UR than most other decks can on metal. Very few other decks get anywhere near.